Journal of Paleontology, page 1 of 23 Copyright © The Author(s), 2022. Published by Cambridge University Press on behalf of The Paleontological Society. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited. 0022-3360/22/1937-2337 doi: 10.1017/jpa.2022.23 Morphology and paleobiology of the Late Cretaceous large-sized shark Cretodus crassidens (Dixon, 1850) (Neoselachii; Lamniformes) Jacopo Amalfitano,1* Fabio Marco Dalla Vecchia,2 Giorgio Carnevale,3 Eliana Fornaciari,1 Guido Roghi,4 and Luca Giusberti1 1 Dipartimento di Geoscienze, Università degli Studi di Padova, Padova I-35131, Veneto, Italy 2 Institut Català de Paleontologia (ICP), Universitat Autònoma de Barcelona, Cerdanyola del Vallès E-08193, Catalunya, Spain 3 Dipartimento di Scienze della Terra, Università degli Studi di Torino, Torino I-10125, Piemonte, Italy 4 Istituto di Geoscience e Georisorse, CNR, Padova I-35131, Veneto, Italy Abstract.—The definition of the Cretaceous shark genus Cretodus Sokolov, 1965 is primarily based on isolated teeth. This genus includes five species. Among these, Cretodus houghtonorum Shimada and Everhart, 2019 is the only species based on a partially preserved skeleton. Here, the taxonomic attribution of a virtually complete skeleton of Cretodus from the Turonian of northeastern Italy is discussed, together with a few specimens from the Turonian of England. One of the latter is investigated through micropaleontological analysis to determine its stratigraphic position. The material is referred to Cretodus crassidens (Dixon, 1850), the diagnosis of which is emended herein. The dentition is tentatively recon- structed, exhibiting strong similarities with congeneric species, although it differs in having strong vertical folds on the main cusp labial face, a mesiodistally broad tooth aspect, weak and well-spaced ‘costulae’ at crown base, and a dif- ferent dental formula in the number of parasymphyseal and lateral rows. Some tooth malformations are interpreted as feeding-related or senile characters. The Italian specimen suggests that Cretodus crassidens had a wide and laterally expanded mouth and head, a stout body, and attained a gigantic size. Cretodus crassidens was a moderate-speed swim- ming shark ecologically like the extant tiger shark Galeocerdo cuvier (Péron and Lesueur in Lesueur, 1822). The age estimate from vertebral-band counting suggests that the Italian individual was at least 23 years old and the growth model indicates a longevity of 64 years and a maximum attainable total length of 9–11 m. Cretodus crassidens occurs both in Boreal and Tethyan domains, implying a broad paleobiogeographic distribution and a preference toward offshore settings. Introduction of turtle bones alongside the vertebral column of the shark, which was interpreted as its gastric content. Based on dental The extinct shark Cretodus Sokolov, 1965, like many other characters, Shimada and Everhart (2019) considered the speci- extinct chondrichthyans, was defined based on isolated teeth men discussed by Amalfitano et al. (2017a) to be conspecific collected from Upper Cretaceous (Cenomanian–Turonian) mar- with, or closely allied to, Cretodus crassidens. The attribution ine deposits from all over the world (Cappetta, 2012). However, to Cretodus crassidens is confirmed herein based on a detailed this large lamniform is also represented by associated skeletal analysis of the Italian specimen and further supported by add- remains recently reported from the middle-upper Turonian Sca- itional information and comparison with other material, includ- glia Rossa of Veneto, northeastern Italy (Amalfitano et al., ing the holotype, from the English Chalk Group of southern 2017a) and from the middle Turonian Blue Hill Shale Member England, UK. A tentative reconstruction of the dentition of of the Carlile Shale of Kansas, USA (Shimada and Everhart, this species is also provided here, together with a discussion 2019). The partial skeleton from Kansas was assigned to a on several paleobiological traits of the species. new species, Cretodus houghtonorum Shimada and Everhart, 2019, whereas the Italian specimen has been regarded since its Geological setting discovery as close to Cretodus crassidens (Dixon, 1850). Amal- fitano et al. (2017a) prudently referred the Italian specimen to The geological setting of the ‘Lastame’ lithofacies of the Scaglia Cretodus sp. in a study focused on a pellet-like accumulation Rossa of the Lessini Mountains (∼30 km N of Verona, Veneto, Italy; Fig. 1), which yielded the Cretodus remains, has been thoroughly described in a series of papers dealing with the *Corresponding author. remarkable vertebrate assemblage of this Cretaceous Lagerstätte 1 https://doi.org/10.1017/jpa.2022.23 Published online by Cambridge University Press 2 Journal of Paleontology:1–23 Figure. 2. (1) Simplified location map of the English Chalk. Cretaceous rocks at outcrop (dark gray) and concealed (light gray) in England. (2) Lithostrati- graphic chart summarizing the Cenomanian–Turonian formations of the Chalk Group. BGS = British Geological Survey, Fm. = Formation. Modified after Hop- son (2005) and Wilkinson (2011). Figure 1. (1) Simplified location map and lithostratigraphic context of the ‘Lastame’ localities. The quarries are located on Mt. Loffa (Lessini Mountains, Verona Province). (2) Lithostratigraphic chart summarizing Cenomanian–Santo- nian formations of northeastern Italy. ‘Lastame’ spans from Turonian pro parte to Basin and equivalent to the lowest part of the Lewes Nodular Coniacian pro parte. BL = Belluno; PD = Padova; RO = Rovigo; TV = Treviso; VE = Venezia; VI = Vicenza; VR = Verona; * = location of the Benedetti quarry Chalk Formation, the New Pit Chalk Formation, and the Holy- yielding the Italian specimen of Cretodus crassidens; gray = mountain ranges or well Nodular Chalk Formation (with the exclusion of the Plenus hills; white = plains and valleys. Marls Member) in the Southern Province (Hopson, 2005; Wilk- inson, 2011; Gale, 2019; Fig. 2.2). The ‘Middle Chalk’ spans from the upper Cenomanian (only the Plenus Marl Member) (Amalfitano et al., 2017a, b, 2019; Amadori et al., 2019, 2020a, b; to the middle Turonian (Wilkinson, 2011) and yielded remains Palci et al., 2013). The 7 m thick nodular/subnodular interval of of numerous fossil fish taxa, although the number of vertebrates whitish and pinkish-reddish limestones of the Scaglia Rossa per volume of rock is very low (Mantell, 1822; Woodward, extensively quarried in Verona Province is characterized by 1902, 1903, 1907, 1908, 1909, 1911, 1912; Kriwet, 2002; Fried- abundant echinoids, inoceramids, ammonoids, and rudists, but man et al., 2016); the ichthyofauna therein includes a large var- also by vertebrate remains, e.g., lamniform sharks, scleror- iety of bony fishes (e.g., Dixon, 1850; Woodward, 1902, 1903, hynchiforms, bony fishes, marine turtles, and mosasaurs. The 1907, 1908, 1909, 1911, 1912; Kriwet, 2002) and several cartil- Lastame spans from Turonian p.p. to Coniacian p.p. (e.g., aginous fishes (e.g., Cretoxyrhina and Ptychodus; Dixon, 1850; Cigala-Fulgosi et al., 1980; Trevisani and Cestari, 2007; Walli- Woodward, 1902, 1903, 1907, 1908, 1909, 1911, 1912; Long- ser and Schöne, 2020), but most of the vertebrate skeletons and bottom and Patterson, 2002). partial remains so far investigated comes from the middle-upper Turonian interval (e.g., Amalfitano et al., 2017a, b, 2019; Materials and methods Amadori et al., 2020a, b). The Cretodus remains from southern England (UK) exam- The material studied herein consists of a partial articulated skel- ined herein come from the Upper Cretaceous Chalk of Kent eton (101 teeth, two segments of 86 disconnected and coin- (especially near the town of Lewes; Fig. 2.1) and surrounding stacked vertebral centra and fragments of cranial mineralized counties. The associated remains are referred to the classic ‘Mid- cartilage) from the Scaglia Rossa exhibited at the Paleonto- dle Chalk Group’ of southern England (Hopson, 2005). This logical and Prehistorical Museum ‘Don Alberto Benedetti’ unit is part of the Chalk Group, specifically the White Chalk (Museo Paleontologico e Preistorico) of Sant’Anna d’Alfaedo, Subgroup, deposited in the northwestern part of the Anglo-Paris Verona Province, Italy (MPPSA IGVR 91032) and some https://doi.org/10.1017/jpa.2022.23 Published online by Cambridge University Press Amalfitano et al.—Morphology and paleobiology of the shark Cretodus crassidens 3 specimens from the Chalk Group of southern England (UK). right side. Tooth numbering of MPPSA IGVR 91032 in the The English material includes a disturbed tooth set with a single text, figures, and tables is consistent with that of Amalfitano vertebral centrum housed at the Booth Museum of Natural His- et al. (2017a, fig. 6). Some correction of the tooth measurements tory of Brighton, England, UK (BMB 007312), and a disarticu- of MPPSA IGVR 91032 and new tooth measurements of BMB lated tooth set (NHMUK PV OR 25786) and several isolated 007312 are provided in Appendices 1 and 2. teeth that belong to the collections of The Natural History Except for the uninformative calcified cartilage fragments, Museum of London (NHMUK PV OR 25823 [holotype of Cre- the morphology of each anatomical element is described and fig- todus crassidens], 41704, 49951, 44623, and NHMUK PV P ured in detail herein. Terminology and abbreviations follow 4577, 5402, 11144, 12368, 12860, 12870). usual standards for shark teeth, placoid scales, and vertebral cen- The specimens were photographed using a Nikon D810 tra (e.g., Ridewood, 1921; Shimada, 1997a, b, c; Siversson, 1999; camera with a 60–90 mm lens and a Canon PowerShot SX720 Cappetta, 2012; Newbrey et al., 2015; Shimada and Everhart, HS. Measurements were retrieved through the image analysis 2019). Nevertheless, the symphyseal teeth sensu Shimada and software ImageJ (https://imagej.nih.gov/ij/, v. 1.6; Schneider Everhart (2019) are referred herein as parasymphyseal teeth, et al., 2012). Images and interpretative drawings of the speci- and the intermediate teeth from the same paper as third anterior mens were produced using the free software packages GIMP teeth following Siversson’s (1999) terminology. In the literature (GNU Image Manipulation Program, https://www.gimp.org/, of fossil lamniforms, teeth near the symphysis have been con- v. 2.10.6) and Inkscape (https://inkscape.org/, v. 0.92). The syn- sistently addressed as symphyseal teeth (e.g., Siversson, 1999; onymy list follows the standards proposed by Matthews (1973) Shimada, 2002). However, Lamniformes all lack symphyseal and include selected synonyms directly referring to the material teeth (Smith et al., 2013), therefore the erroneous use in dental described herein. The growth model was reconstructed using the nomenclature of symphyseal teeth in Lamniformes should be software package Past 3.26 (https://past.en.lo4d.com/windows; replaced by the term parasymphyseal teeth, already used in Hammer et al., 2001) and plotted with the Desmos graphing other papers (e.g., Cook et al., 2011; Siversson et al., 2013). software (https://www.desmos.com/). The intermediate position sensu Applegate (1967) refers to The reconstruction of the dentition of Cretodus crassidens teeth arising from the area (intermediate bar) between the hol- provided herein is based on the disarticulated dentition of the Ital- lows (bullae) where the other teeth accommodate in the odontas- ian specimen MPPSA IGVR 91032, therefore might be subject to pidid dentition, but the majority of lamniforms do not exhibit biases such as taphonomic or preparation loss and interpretation this condition, having two separate hollows in the upper jaw bias. Specimen MPPSA IGVR 91032, in fact, was discovered without teeth on the intermediate bar and a single hollow in between 1996 and 1997 by quarry owners Giovanni and Gian- the lower jaw (e.g., Siversson, 1999). franco Benedetti and was prepared by Giovanni Benedetti in A least square linear regression method was applied to the 2003 (Amalfitano et al., 2017a). According to the preparator, vertebral centrum length data to estimate the original vertebral the two slabs come from the same layer and were separated by count of the shark and to provide a length estimate of MPPSA a karst fissure; thus, the skeletal remains in the two slabs should IGVR 91032 (modelled in Past 3.26, Supplemental Data 1; belong to the same individual. Nevertheless, the two slabs differ data from Amalfitano et al., 2017a, appendix B). Tooth size is slightly in color and the different sizes between the last vertebral usually employed as a parameter to infer total length of a fossil centrum on the main slab and the first centrum on the second slab or extant shark, considering both crown or tooth height (e.g., suggest that several vertebrae are missing between the two seg- Gottfried et al., 1996; Shimada, 2003, 2019) and tooth width. ments (Amalfitano et al., 2017a). Furthermore, the vertebrae on Tooth width exhibits less variability than crown height (Bass the second slab are all glued. Most of the teeth (∼70%) detached et al., 1975) and thus has been considered more reliable by sev- from slab A when it was exposed by quarry works or remained eral authors (e.g., Newbrey et al., 2015; Perez et al., 2021). In attached to the counterslab (now missing); they were glued onto this paper, we considered both methods, despite that the total the slab later and mostly not in their exact original position jaw width method is not directly applicable because of poor (some might be lost). However, the glued teeth undoubtedly preservation of most of the tooth roots in the sample considered belong to this specimen because their morphological characters herein. Length estimates are provided using the equation by Shi- are identical to the in-situ teeth (Amalfitano et al., 2017a). The mada and Everhart (2019) that exploits the theoretical linear teeth are figured only on the labial side or the lingual side because relationship of crown height (CH) and total length (TL) for most of them are still embedded in the sedimentary matrix or were Cretoxyrhina mantelli (see Shimada, 2008, fig. 5): glued after detaching and are exposed mainly on one side. Chem- ical or physical preparation to separate the teeth from the matrix TL(cm) = 12.5 × CH(mm) (1) (e.g., Siversson et al., 2007), as well as sectioning the vertebral centra (e.g., Newbrey et al., 2015; Shimada and Everhart, However, Shimada et al. (2020) provided a more conservative 2019), was not possible because the specimen is subject to Italian estimate based on the linear function: cultural heritage care laws and cannot be altered without special permission. Ammonium chlorite coating of the teeth (e.g., Sivers- son et al., 2007; Amadori et al., 2019) was also not performed TL(cm) = 11.784 × CH(mm) - 0.331 (2) because of technical issues related to the position and size of the specimen in the Museum exhibition. Teeth in the reconstruc- with CH of any anterior tooth in any given non-Alopias macro- tion are illustrated from the left side of the jaws and missing phagous lamniform taxon, although this possibly underesti- elements were filled with mirrored images of teeth from the mated the body total length. https://doi.org/10.1017/jpa.2022.23 Published online by Cambridge University Press 4 Journal of Paleontology:1–23 Using the definition of bite circumference sensu Lowry et al., 2021) and has proven to be a viable approach to attempt et al. (2009) to bypass the lack of a reliable total jaw width to explore the growth pattern of extinct elasmobranchs, although and applying the reverse of their formula: with the obvious limits dependent from the restricted sample. Parameters obtained from the VBGF and other derived measure- ments are applied with equations from Natanson et al. (2006) for log(bite ‘circumference’[mm]) longevity to discuss and compare the results of the analyses. = 1.007 × log(TL[ mm]) - 0.8 (3) Specimen BMB 007312 is still embedded in Chalk soft matrix. The matrix was hence collected as powdered residual for the great white shark Carcharodon carcharias (Linnaeus, fallen from the specimen after simple handling. The sample 1758), it is possible to have a TL estimate of Cretodus crassidens was prepared as unprocessed material on a smear slide and also from the arch-like arrangement of teeth in specimen MPPSA examined under a light microscope at 1250X magnification to IGVR 91032 (geometrical approximation in Supplemental Data 2). establish the stratigraphic position of the specimen. The calcar- An attempt to assess the growth pattern of the fossil shark eous nannofossil content of the samples was analyzed with using the von Bertalanffy growth function (VBGF; von Berta- semiquantitative methods (three vertical traverses corresponding lanffy, 1938) is proposed below. The VBGF has been widely to 6–7 mm2) following Gardin and Monechi (1998). used to describe the growth of fish (Haddon, 2001). This func- Repositories and institutional abbreviations.—Types, figured, tion was specifically used as a quantitative method to describe and other specimens examined in this study are deposited in the growth of extant elasmobranchs based on growth bands on the following institutions: Booth Museum of Natural History calcified structures such as vertebral centra (e.g., Cailliet and of Brighton, UK (BMB); Sternberg Museum of Natural Goldman, 2004; Goldman, 2004). The method has also been History, Fort Hays State University, Hays, Kansas, USA applied to some extinct sharks (e.g., Shimada, 2008; Cook (FHSM); Museo Paleontologico e Preistorico di Sant’Anna et al., 2011; Newbrey et al., 2015; Shimada and Everhart, d’Alfaedo, Verona, Italy (MPPSA IGVR); and The Natural 2019; Jambura and Kriwet, 2020; Shimada et al., 2021). The History Museum, London, UK (NHMUK). VBGF provides the best fit for species with slow growth and extended longevity (maximum total length >100 cm of total Systematic paleontology length and 0.02 < k < 0.25 yr–1, where k is the growth coeffi- cient), such as large pelagic sharks (Liu et al., 2021). It must Class Chondrichthyes Huxley, 1880 be mentioned that conventional VBGF analyses uses independ- Subclass Elasmobranchii Bonaparte, 1838 ent measurements from a dataset with many random samples Cohort Euselachii Hay, 1902 from a population. The VBGF method applied here exploits ori- Subcohort Neoselachii Compagno, 1977 ginal and derived measurements (Table 1) from a single but best- Order Lamniformes Berg, 1958 preserved specimen, that would be considered dependent mea- Family Pseudoscapanorhynchidae Herman, 1979 (sensu surements. This exploratory method has been recently applied Siversson and Machalski, 2017) in other papers (e.g., Shimada and Everhart, 2019; Shimada Genus Cretodus Sokolov, 1965 (sensu Shimada and Everhart, 2019) Table 1. Raw measurements (BN, CR) and derived measurements (pCR, TL1, TL2, and CH) based on a vertebral centrum of Cretodus crassidens (Dixon, Type species.—Otodus sulcatus Geinitz, 1843; ‘unterer Pläner 1850) (MPPSA IGVR 91032; Fig. 11). BN = band pair number; CH = crown ( plenus-marl), upper part of upper Cenomanian, Plauen, height; CR = center radius; pCR = percentage of center radius; TL = total length. Saxony, Germany. BN CR (mm) pCR (%) TL1 (cm) TL2 (cm) CH (mm) Cretodus crassidens (Dixon, 1850) 0 10.7 21.5 141.9 167.7 12.0 1 14.1 28.5 187.8 221.9 15.9 Figures 3–10 2 16.9 34.0 224.3 265.1 19.0 3 19.4 39.1 258.1 305.0 21.9 Selected synonymy: 4 21.4 43.2 285.1 336.9 24.2 5 23.5 47.3 312.1 368.9 26.5 6 25.5 51.4 339.1 400.8 28.8 †1850 Oxyrhina crassidens Dixon, p. 367, pl. 31, figs. 13, 13A. 7 27.3 55.0 362.8 428.7 30.8 1889 Oxyrhina crassidens; Woodward, p. 382. 8 29.1 58.6 387.1 457.5 32.8 9 30.8 62.1 410.0 484.6 34.8 1911 Oxyrhina crassidens; Woodward, p. 205, pl. 44, figs. 1, 2. 10 32.7 65.8 434.4 513.4 36.9 1987 Cretodus crassidens; Cappetta, p. 98. 11 34.5 69.5 458.7 542.1 38.9 12 36.5 73.6 485.7 574.0 41.2 2012 Cretodus crassidens, Cappetta, p. 255. 13 38.0 76.5 504.6 596.4 42.8 2017a Cretodus sp.; Amalfitano et al., p. 109, figs. 2, 4, 6–9, 15. 14 39.2 78.9 520.8 615.5 44.2 2019 Cretodus crassidens; Shimada and Everhart, p. 4, fig. 15 40.7 82.0 541.1 639.5 45.9 16 42.4 85.5 564.1 666.6 47.9 9A–P. 17 44.4 89.4 589.8 697.0 50.0 18 45.3 91.2 601.9 711.3 51.1 19 46.3 93.2 615.4 727.3 52.2 Holotype.—NHMUK PV OR 25823 (isolated tooth). 20 47.2 95.1 627.6 741.7 53.2 21 48.0 96.7 638.4 754.5 54.2 22 48.7 98.2 647.8 765.6 55.0 Diagnosis (emended).—A Cretodus species that differs from all 23 49.6 100.0 660.0 780.0 56.0 other species of the genus by teeth with mesiodistally broad https://doi.org/10.1017/jpa.2022.23 Published online by Cambridge University Press Amalfitano et al.—Morphology and paleobiology of the shark Cretodus crassidens 5 Figure 3. Partial articulated skeleton of Cretodus crassidens (Dixon, 1850) from the middle Turonian of the Scaglia Rossa Veneta of northeastern Italy, MPPSA IGVR 91032: (1) Orthophoto of the specimen. The slab embedding the tooth accumulation, the tessellated cartilage elements, the anterior portion of the vertebral column, and the turtle remains is Slab A. The one embedding the caudalmost vertebral centra is Slab B. (2) Interpretative drawing of (1). (3) Interpretative drawing of the tooth accumulation. Teeth in situ are indicated (yellow in electronic version), with tesselated cartilage elements (dark gray) and anteriormost vertebral centra (light gray). Scale bars = 1 m (1, 2), 20 cm (3). https://doi.org/10.1017/jpa.2022.23 Published online by Cambridge University Press 6 Journal of Paleontology:1–23 aspect (crown width to 82% of crown height even in a2), slightly Materials.—NHMUK PV OR 25786 (disarticulated tooth set, ogival to triangular main cusp, with vertical strong folds and sensu Shimada, 2005), 41704, 49951, 44623; NHMUK PV P deep grooves on the labial face, weak and well-spaced basal 4577, 5402, 11144, 12368, 12860, 12870; BMB 007312 crown ‘costulae’ (or ‘striae’) on labial and lingual faces, (disturbed tooth set, sensu Shimada, 2005); MPPSA IGVR robust lateral cusplets (lateral cusplet height ∼25–55% of 91032. crown height), sinusoid to parabolic crown base and sinusoid to parabolic basal concavity. Aberrant lateral cusplets can be Remarks.—The dental characters of the specimens described present or replaced by weakly crenulated heels on the above are fully consistent with the diagnosis of Cretodus shoulders of the main cusp or rounded papillae. proposed by Shimada and Everhart (2019). In this paper, an emended diagnosis is introduced specifying new details Occurrence.—The type locality is Houghton, Sussex (England, observed on the materials analyzed. UK); the stratigraphic horizon is the ‘Middle Chalk,’ Turonian. All other English specimens come from localities of the ‘Middle The anatomy of Cretodus crassidens Chalk’: Lewes, Sussex, and Whyteleafe, in Surrey (England, UK), although the exact geospatial coordinates are not known. Teeth.—Some of the most representative teeth are illustrated in The Italian specimen comes from the ‘Lastame’ lithofacies of Figure 4; a reconstruction of the dentition is illustrated in Scaglia Rossa Veneta (middle-upper Turonian) of Mt. Loffa, Figure 7. Here follows a description of general dental Sant’Anna d’Alfaedo (Lessini Mountains, Veneto, Italy), characters and an interpretation of the tooth pattern within the specifically from Benedetti Quarry (45.6°N, 10.9°E). upper and lower series, considering that the specimen IGVR The matrix obtained from BMB 007312 contains abundant 91032 preserves a largely disarticulated dentition. and well-preserved calcareous nannofossils. The assemblage is General characters.—Teeth mesiodistally broad (crown well-diversified and contains 13 specimens of Lucianorhabdus width to 82% of crown height even in anterior teeth, specifically maleformis Reinhardt, 1966, four specimens of Quadrum gart- a2), with main cusp and a pair of large lateral cusplets, the mesial neri Prins and Perch-Nielsen in Manivit et al., 1977 in ∼6 mm2, one divergent and the distal one slightly convergent with respect that, together with the absence of Eiffellithus eximius s.s. Huber to main cusp (can be divergent in some teeth). Main cusp is mas- et al., 2017 (only one uncertain specimen) and Lucianorhabdus sive, slightly ogival to triangular, with strong vertical folds and quadrifidus Forchheimer, 1972, are indicative of the Biozone two to five deep grooves on labial face. Lateral teeth have tri- UC 7 of Burnett (1999). The corresponding interval would be angular main cusp. Lateral cusplets are well separated from lower-middle Turonian. Correlation with the foraminiferal main cusp but connected on labial side with basally extended zonation of the Chalk Group allows assignment of the sample crown base on both root lobes. Numerous, regularly and well- to the Helvetoglobotruncana helvetica Biozone and possibly spaced, well-marked, and very short vertical grooves and ridges the lower part of the Marginotruncana sigali Biozone, corre- (‘costulae’ or ‘striae’) are present at crown base on both labial sponding to the British Geological Survey (BGS) Zones 9–10 and lingual sides, more marked on labial side. Cutting edges (Wilkinson, 2011; Huber et al., 2017). Based on biostratigraphic are usually continuous and sharp, connecting main cusp and data, the sample is placed between the middle-upper part of the cusplets. Mesial root lobe is usually slightly pointed, whereas Holywell Nodular Chalk Formation and basal part of the New distal lobe is more expanded and rounded. Labial face of root Pit Chalk Formation. is flat or slightly recessed at crown base. Lingual face of root is overall swollen and bulgy, with lingual protuberance (more Description.—The English specimens include mainly isolated evident and protruding in parasymphyseals, anteriors, and teeth, previously reported by Woodward (1911) under various mesialmost laterals). Lateral teeth exhibit more splayed root names. There are also several associated specimens: the lobes than parasymphyseals and anteriors. disarticulated tooth set NHMUK PV 25786 (including seven Upper dentition.—Upper teeth are labiolingually thick, disarticulated teeth), the disturbed tooth set BMB 007312 and massive, and almost straight, with convex labial and lingual the Italian specimen MPPSA IGVR 91032 (Figs. 3, 4, 8–11). faces and tip slightly turned outward in certain specimens. Cut- The English specimen BMB 007312 includes 18 teeth, nine ting edges are straight and continuous. Crown base and basal still embedded in matrix, associated with two vertebral root concavity are deeply sinusoid (especially in anterior centra, one fragmentary and the other complete and teeth). Root-lobes angle is acute in parasymphyseals and ante- undeformed, characterized by maximum diameter 95 mm and riors, and is right in laterals. Root lobe apices are directed thickness ∼40 mm; this specimen was possibly reported as ‘a basally. The upper dentition includes two parasymphyseal small group of associated teeth from Lewes’ by Woodward rows, three anterior rows, and at least 10 lateral rows, but a (1911, p. 206; Figs. 5, 6). The Italian specimen MPPSA IGVR large gap is present after L8 (possibly two missing rows). Dis- 91032 is a virtually complete articulated skeleton that includes tinctive characters of tooth rows are: 120 teeth, 86 vertebral centra, as well as fragments of cranial mineralized cartilage. This specimen also preserves placoid scales retrieved from residues processed from matrix samples, (1) Upper parasymphyseal teeth (P): Main cusp is rather slender and includes a circular accumulation of bones of a marine turtle (PCH-PCW ratio 1.4–1.5). P1 exhibits a mesially curved alongside the shark vertebral column, interpreted as a gastric main cusp. P2 almost straight and is the smallest among pellet (Amalfitano et al., 2017a). Dental characters and other these teeth. The height of the lateral cusplet represents morphological features are described in detail below. 32% of crown height. https://doi.org/10.1017/jpa.2022.23 Published online by Cambridge University Press Amalfitano et al.—Morphology and paleobiology of the shark Cretodus crassidens 7 Figure 4. Selection of representative teeth of Cretodus crassidens (Dixon, 1850) from the middle Turonian of the Scaglia Rossa Veneta of northeastern Italy, MPPSA IGVR 91032: (1) first upper parasymphyseal tooth (no. 16), labial view; (2) first lower parasymphyseal tooth (no. 22), labial view; (3) first upper anterior tooth (no. 37), labial view; (4) second lower anterior tooth (no. 3), labial view; (5) second lower anterior tooth (no. 11), lingual view; (6) second upper anterior tooth (no. 13), labial view; (7) third upper anterior tooth (no. 53), labial view; (8) third lower anterior tooth (no. 24), labial view; (9) first lower lateral tooth (no. 62), labial view; (10) third lower lateral tooth (no. 59), labial view; (11) sixth upper lateral tooth (no. 20), lingual view; (12) fourth upper lateral tooth (no. 61), labial view; (13) seventh lower lateral tooth (no. 103), lingual view; (14) eighth lower lateral tooth (no. 94), labial view; (15) ninth lower later tooth (no. 92), lingual view; (16) com- missural upper lateral tooth (no. 104), labial view. Numbers match those used by Amalfitano et al. (2017a, fig. 6). Scale bar = 20 mm. https://doi.org/10.1017/jpa.2022.23 Published online by Cambridge University Press 8 Journal of Paleontology:1–23 Figure 5. Associated remains of Cretodus crassidens (Dixon, 1850) from the lower Turonian of the Chalk Group of England, BMB 007312: (1, 2) blocks with embedded teeth; (3, 4) complete vertebral centrum in frontal and dorsal views; (5) two fragments of a partial vertebral centrum in frontal view; (6) isolated teeth from the same tooth set (second one from left in labial view, all others in lingual view). Scale bars = 50 mm. https://doi.org/10.1017/jpa.2022.23 Published online by Cambridge University Press Amalfitano et al.—Morphology and paleobiology of the shark Cretodus crassidens 9 (2) Upper anterior teeth (A): A1 is reduced (maximum inflated aspect. Root-lobes angle is almost right in parasymphy- observed height 51 mm) and strongly oblique distally (21° seals and anteriors, obtuse in laterals. Root-lobes apices slightly referring to the vertical axis). A2 and A3 have almost diverge. Lower dentition includes a single parasymphyseal row, upright and apparently symmetrical main cusps; A2 is three anterior rows, and at least eight lateral rows, with a gap in imperceptibly slanted mesially, and A3 distally. These the posteriormost positions, including commissural teeth. Dis- teeth are rather large (A2 is 61 mm total height, the largest tinctive characters of tooth rows are: one of upper anteriors) and slender (TH-TW ratio 1.3–1.4). The root lobes of A1 are less splayed with respect to those of the adjacent teeth and U-shaped. The height of the lateral (1) Lower parasymphyseal teeth (p): These two teeth have a cusplet is ∼28–33% of crown height. rather symmetric outline and slender main cusp (PCH-PCW (3) Upper lateral teeth (L): Main cusp slightly to strongly dis- ratio 1.3). Lateral cusplets are strongly divergent. The lateral tally oblique. Their maximum height ranges from 48 to cusplet height is ∼21–26% of crown height. 16 mm. L1-L3 teeth have an almost upright main cusp, (2) Lower anterior teeth (a): These are the largest teeth in the from L4 onward the inclination becomes more evident. dentition (a1 is 67 mm high, whereas a2 is 69 mm high, L11?-L12? possibly represent the commissural teeth. although incompletely mineralized; in this case it could Teeth are generally larger than high except for the first be higher; 56 mm high in crown height). Tooth a1 is more three, with L2 representing the highest tooth (like in many symmetrical than a2, which is slightly slanted in distal dir- other lamniforms; Shimada, 2002); lateral cusplet height ection. Main cusp of a2 bears four deep enameloid folds on is 35–54% of crown height, with the ratio increasing toward the labial face extending for almost its entire height. Tooth the commissural rows. Root lobes become generally more a2 enlarged (crown width to 82% of crown height). Lateral divergent distally. cusplets height is 25–31% of crown height (similar to upper anterior ratio). Tooth a3 is rather large (60 mm TH in functional row), with main cusp slightly bent distally and Lower dentition.—Lower teeth have a sigmoid profile divergent cusplets. Tooth as high as wide (TH-TW ratio (labiolingual direction), nearly flat labial face, and convex lin- 1.18–1.02). Lateral cusplet height is ∼29% of crown height. gual face; the tip has a reversed curvature, so that although (3) Lower lateral teeth (l): Main cusp is almost upright to most of the crown is curved inward toward the mouth cavity, slightly oblique. The inclination of the cusp increases dis- the tip is turned outward (as also observed in other sharks; Fraz- tally. Total height ranges 32–53 mm, but this range does zetta, 1988), which confers a more labiolingually compressed not include the distalmost rows (which comprises teeth and curved aspect with respect to the upper teeth. Main cusp with crown height measuring 22 mm, l7, and 17 mm, l8). of lower teeth is generally mesiodistally broader than those of Teeth l1–l4 are almost as large as high, with almost upright upper teeth. Crown base and root concavity are shallow and cusps. Observing the size of l8 compared with those of the more parabolic than those of upper teeth. Cutting edges are sig- corresponding upper laterals, it is possible to suggest that moid in profile. Crown base slightly overhangs the upper portion there are at least four missing rows in the commissural of the root, creating a shallow recess and conferring a slightly part of the lower dentition. Lateral cusplet height represents Figure 6. Second lower anterior tooth of Cretodus crassidens (Dixon, 1850), BMB 007312: (1) labial view; (2) mesial view; (3) distal view; (4) lingual view. Arrow indicates a dental malformation (crenulation on the cutting edge between the distal cusplet and the main cusp). Scale bar = 50 mm. https://doi.org/10.1017/jpa.2022.23 Published online by Cambridge University Press 10 Journal of Paleontology:1–23 Figure 7. Interpretation of the dentition pattern in Cretodus crassidens (Dixon, 1850), based on specimen MPPSA IGVR 91032. Numbers in gray match those used by Amalfitano et al. (2017a, fig. 6). * = mirrored right teeth; dotted lines = reconstructed portions of the teeth based on other teeth in the sample; ? possibly missing tooth rows; // = gaps in the reconstruction. Scale bar = 50 mm. Figure 8. Vertebral centra of Cretodus crassidens (Dixon, 1850), MPPSA IGVR 91032: (1) interpretive drawing of slabs, with glued vertebral centra in dark gray; (2) exposed articular surface of corpus calcareum; (3) exposed intermedialia showing pattern of calcification of the vertebral centrum, showing radial and concentric lamellae patterns; (4) lateral side of vertebral centra exhibiting septae. Black and white scale bars in centimeters. https://doi.org/10.1017/jpa.2022.23 Published online by Cambridge University Press Amalfitano et al.—Morphology and paleobiology of the shark Cretodus crassidens 11 incremental growth bands. These bands are not easily discernable on the vertebral centra of BMB 007312, probably due to erosion. In MPPSA IGVR 91032, a vertebral centrum deprived of the articular surface of the corpus calcareum due to biostratinomic processes (Fig. 8.3) presents concentric lamellae in the intermedialia and radial lamellae that are moderately thick (∼1 mm). The radial lamellae tend to branch near the half of the radius length, enlarging and merging into composite and thick longitudinal septae toward the centrum periphery. The longitudinal septae, visible in lateral view in both MPPSA IGVR 91032 and BMB 007312 (Figs. 5.4, 8.4), are well-spaced with low density along the lateral surface of the centrum, separated by large fossae (∼20 mm wide), except for the dorsal and ventral sides of the centrum, which exhibit a higher density of septae (three or four in an interval of ∼20 mm). Diagonal or transverse septae are absent. Articular foramina are visible on some centra from MPPSA IGVR 91032 but are better visible on the complete vertebral centrum of BMB 007312, being more oval and larger than adjacent fossae (Figs. 5.4, 8.4). Tessellated cartilage elements.—Seven main fragments of tessellated calcified cartilage are present on slab A of MPPSA IGVR 91032. Four occur close to each other at one extremity of the tooth accumulation and three are glued within the turtle Figure 9. Placoid scales of Cretodus crassidens (Dixon, 1850), MPPSA IGVR remains. These tessellated cartilage elements probably split 91032: (1) tricuspid placoid scale, in frontal, lateral, and posterior views; (2) sin- away from the slab during removal of the counterslab and gle cusp placoid scale, in frontal, lateral, and posterior views; (3) rounded cusp have erroneously been glued to the turtle remains (Amalfitano placoid scale, in frontal, lateral, and posterior views. Scale bar = 500 μm. et al., 2017a). The fragments are flat and range 55–130 mm in length and 40–85 mm in width. Their exposed surface shows the striated texture corresponding to the underlying polygonal ∼25–53% of crown height, with the ratio increasing toward prisms (tesserae; Dingerkus et al., 1991; Dean and Summers, the distalmost rows. 2006), which are well recognizable in the damaged areas. One of the fragments close to the tooth accumulation still has Vertebral column.—MPPSA IGVR 91032 comprises only 86 a lateral tooth associated (Fig. 3.3). The presence of a vertebral centra, 51 on slab A and 35 on slab tooth rooted into one of the fragments further indicates that B. Measurements were provided by Amalfitano et al. (2017a, the fragment is part of the palatoquadrate or Meckel’s appendix B). Centra on slab A are partially articulated and cartilage, possibly a commissural portion considering the represent the anterior part of the vertebral column (Figs. 3.1– tooth size. 3.2, 8.1). Centra on slab B are artificially aligned and decrease in size posteriorly (Figs. 3.1–3.2, 8.1). Vertebral centra are Placoid scales.—Placoid scales (or dermal denticles) that round, with height equal to width (Fig. 8.2). The sizes of the covered the body of Cretodus crassidens are common in the last centrum on slab A and the first centrum on slab B differ reddish calcareous marly limestone embedding MPPSA IGVR by ∼20 mm, suggesting that a portion of the vertebral column 91032. They appear as whitish submillimetric prisms in the between the two segments is missing (Amalfitano et al., reddish rock. They are usually composed of a base, with a 2017a). This is also indicated by the low vertebral count (86). nutrient foramen at the bottom, and a crown (Fig. 9). The base The diameter of the centra on slab A ranges from 115 mm is often missing because it is delicate and is easily damaged (vertebra 16) to 53 mm (vertebra 1); that on slab B ranges by the action of the acid used to dissolve the limestone to from 79 mm (first centrum of the slab) to 28 mm (last three isolate them (Amalfitano et al., 2017a). Placoid scale height centra) (Amalfitano et al., 2017a, appendix B). The mean ranges 1–0.3 mm and width 0.6–0.3 mm. It was not possible length of the vertebral centra is ∼32.5 ± 6.22 mm (Amalfitano to determine how the placoid scales were originally et al., 2017a, appendix B). The centra are well-calcified and distributed. All scales are ornamented with strong parallel structurally match the definition of ‘lamnoid vertebrae’ (sensu basoapical ridges and plications on the convex anterior face of Applegate, 1967, p. 62; Fig. 8.2–8.4). Many centra of MPPSA their crown; ridges and plications do not extend posteriorly IGVR 91032 suffer slight taphonomic distortion and some are and have different sizes (from broad to slender) and general incomplete, whereas a single one of BMB 007312 is nearly shapes (e.g., rhomboid, Fig. 9.1, 9.2; rounded or drop-like, intact. The articular surface of the corpus calcareum is devoid Fig. 9.3). Except for some tricuspid scales (Fig. 9.1), the cusp of any kind of ornamentation and generally exhibits ∼20 is usually single, varying usually from pointed to rounded in prominent concentric rings that are interpreted to be annual shape (Fig. 9.2, 9.3). https://doi.org/10.1017/jpa.2022.23 Published online by Cambridge University Press 12 Journal of Paleontology:1–23 Figure 10. Variability in cusplet number and tooth malformations within the dentition of Cretodus crassidens (Dixon, 1850), MPPSA IGVR 91032: (1) tooth no. 10: the right shoulder of the central cusp has a crenulated cutting edge, whereas the other (arrows in detail view) bears a cusplet with two additional cuspules (a tricuspid cusplet); (2) tooth no. 24: the cutting edge between the main cusp and the cusplet has an accessory papilla (arrow in detail view); (3) tooth no. 33: cutting edge between the main cusp and the left cusplet has an accessory papilla (arrow in detail view); (4) tooth no. 35: smaller accessory cusplet occurs mesial to the mesial cusplet (arrow in detail view); (5) tooth no. 7: smaller accessory cusplet occurs mesial to the mesial cusplet (arrow in detail view); (6) tooth no. 32: left cusplet (arrow in detail view) is much smaller than the right cusplet; (7) tooth no. 10: right shoulder of the main cusp has an irregularly crenulated heel (the cusplet is absent; arrows in detail view), whereas the left shoulder has a cusplet with two additional cuspules (tricuspid cusplet); (8) tooth no. 47: the main cusp is bent lingually and the right cusplet is enlarged, bulky, and recurved lingually (arrow in main view; detail view is from the side); (9) tooth no. 58: right distal cusplet is enlarged and high; a distal slice of the main cusp grew independently and has its own apex (arrow in detail view); (10, 11) tooth no. 66 in labial and lateral view: the main cusp is partially twisted; its upper part is blunt and bears a diminutive and demarcated apex (arrow). Numbers matching those used by Amalfitano et al. (2017a, fig. 6). Scale bars = 10 mm. https://doi.org/10.1017/jpa.2022.23 Published online by Cambridge University Press Amalfitano et al.—Morphology and paleobiology of the shark Cretodus crassidens 13 Discussion Shimada and Everhart (2019) clearly distinguished five species of the genus—Cretodus crassidens, Cretodus giganteus Taxonomy.—Genus-level taxonomy was recently commented (Case, 2001), Cretodus houghtonorum, Cretodus longiplicatus upon by Siversson and Machalski (2017, p. 453, 454) and Werner, 1989, and Cretodus semiplicatus—and proposed a Shimada and Everhart (2019). The types of the first two phylogenetic hypothesis recognizing three categories based on described species of Cretodus—Cretodus semiplicatus similarities between the species (‘longiplicatus/semiplicatus- (Münster in Agassiz, 1843) from the Turonian of Germany grade,’ ‘giganteus/houghtonorum-grade,’ and ‘crassidens- and Cretodus crassidens from the Turonian of the UK—are grade’). Based on the original illustration of the holotype of Cre- each based on isolated and poorly preserved teeth (Shimada todus sulcatus (Geinitz, 1843), it is possible that Cretodus long- and Everhart, 2019). The syntypes of Cretodus semiplicatus iplicatus is a junior synonym of Cretodus sulcatus (see are considered marginally diagnostic for their poor Siversson and Machalski, 2017). Cretodus crassidens is easily preservation state and position (lateroposterior tooth, generally distinguished from its congenerics by its mesiodistally broad conservative in morphology among lamniforms and thus less teeth with large main cusp, robust lateral cusplets, and long ver- taxonomically informative; Siversson and Machalski, 2017; tical folds (to two-thirds of CH) and grooves on the labial face, Shimada and Everhart, 2019). Furthermore, being almost especially in anteriormost rows. A rather large main cusp is also coeval, they could be conspecific with the type specimen of present in Cretodus giganteus, but this species seems to be more Cretodus crassidens (see Siversson and Machalski, 2017). related to Cretodus houghtonorum for other characters and dis- Differences in morphology are addressed as dependent on plays a thinner mesiodistal aspect (Shimada and Everhart, different tooth position (syntype of Cretodus semiplicatus 2019). Basal crown ‘costulae’ (or ‘striae’; Shimada and Ever- interpreted as a lower lateroposterior tooth, thus a more hart, 2019) are stronger and wider spaced than those of the posterior position) and ontogenetic stage (Siversson and ‘giganteus/houghtonorum-grade’ (sensu Shimada and Everhart, Machalski, 2017). The type specimen of Cretodus crassidens, 2019) but weaker and less dense than those of the ‘semiplicatus/ a large, robust tooth with crenulated heels and lateral cusplet longiplicatus-grade’ (sensu Shimada and Everhart, 2019) and loss, might indicate a senile, female morphotype (Siversson less evident in large teeth, but the difference is well recognizable and Machalski, 2017). in lateral teeth. Lateral cusplets of Cretodus crassidens also Figure 11. Estimated total length range for Cretodus crassidens (Dixon, 1850), MPPSA IGVR 91032. Gray silhouette indicates the lower limit (660 cm); black silhouette indicates the upper limit (780 cm). Silhouette modified after illustration by O.E. Demuth figured by Cooper et al. (2020, fig. 2D). https://doi.org/10.1017/jpa.2022.23 Published online by Cambridge University Press 14 Journal of Paleontology:1–23 Figure 12. Correlation diagram of mean scale crown width (x axis) and mean ridge distance (y axis). Taxa in the light gray cloud are from the group of fast pelagic hunting sharks, whereas those in the dark gray cloud are from the group of large nearshore predators/moderate speed pelagic predators. Note that the Cretodus cras- sidens mean (star) falls within the cloud of correlation of large nearshore predators and moderate pelagic predators. Diagram modified after Reif (1985). Taxa not otherwise mentioned in the text include: Carcharhinus amblyrhynchos (Bleeker, 1856), Carcharhinus falciformis (Müller and Henle, 1841), Carcharhinus galapa- gensis (Snodgrass and Heller, 1905), Carcharhinus melanopterus (Quoy and Gaimard, 1824), Carcharhinus plumbeus (Nardo, 1827), Isurus oxyrinchus Rafinesque, 1810, Lamna nasus (Bonnaterre, 1788), Prionace glauca (Linnaeus, 1758), and Sphyrna tudes (Valenciennes, 1822). differ from those of Cretodus giganteus by having a more robust taxonomic character (Adnet, 2006; Purdy and Francis, 2007; aspect and divergent mesial and convergent distal cusplets, Belben et al., 2017; Marramà and Kriwet, 2017). whereas both the cusplets of Cretodus giganteus are divergent Comparing the dentition pattern presented herein with that (Shimada and Everhart, 2019). of other Cretaceous lamniform sharks, the lack of specialized The reconstruction of the dentition of Cretodus crassidens intermediate teeth combined with the presence of at least one differs from that of the congeneric Cretodus houghtonorum in upper parasymphyseal file is commonly found in Cretaceous its mesiodistally broad morphology and strong vertical enamel- taxa other than Cretodus (e.g., Archaeolamna Silversson, oid folds; the number of parasymphyseal teeth (‘symphyseal’ of 1992, Cardabiodon Siversson, 1999, Cretalamna Glickman, Shimada and Everhart, 2019), three in the upper dentition and 1958, Cretoxyrhina Glickman, 1958, Haimrichia Vullo, Gui- one in the lower one in Cretodus houghtonorum, two in both not, and Barbe, 2016; Shimada, 1997c, 2007; Siverson, 1999; dentitions in Cretodus crassidens; and the presence of a reduced Cook et al., 2011; Dickerson et al., 2013; Siversson et al., first upper anterior in Cretodus crassidens, although Shimada 2013, 2015; Vullo et al., 2016). The presence of a reduced and Everhart (2019) interpreted it as an upper ‘intermediate’ first upper anterior has been reported in other Cretaceous and (third upper anterior) tooth. The lateral teeth have similarly modern lamniforms (e.g., Alopias Rafinesque, 1810, Carchar- upright cusp, becoming more oblique distally, in both Cretodus ias Rafinesque, 1810, Cardabiodon, Haimrichia, Odontaspis crassidens and Cretodus houghtonorum. The number of lateral Agassiz, 1838; Applegate, 1965; Shimada, 2002; Siversson, tooth rows is different: Cretodus crassidens has at least 10 upper 1999; Vullo et al., 2016). laterals and eight lower laterals, whereas Cretodus houghtonorum Vertebral centra are considered poor in diagnostic charac- has 11 upper laterals and eight lower laterals. Therefore, Cretodus ters in lamniforms, except for a few cases in which their morph- crassidens has the following dental formula: ology has been observed in detail (e.g., Newbrey et al., 2015). Comparing vertebral centrum morphology in Cretodus with that of other neoselachians (Newbrey et al., 2015), Cretodus is 2P 3A 10(+2?)L characterized by distinctive radial lamellae branching and organ- 2p 3a 8(+ 4?)l izing in composite and thick septae toward the periphery of the centrum, divided by large fossae. These structures are different It must be noted that ontogenetic variation could strongly from those observed in other extant and extinct lamniform affect the taxonomy of Cretodus. Tooth size has been variously sharks and could represent a genus- or family-level diagnostic addressed as dependent on ontogenetic stage and dietary shifts character. However, a family-level taxonomic discussion is during ontogeny, and care must be taken when using it as well beyond the scope of this paper and needs further evidence https://doi.org/10.1017/jpa.2022.23 Published online by Cambridge University Press Amalfitano et al.—Morphology and paleobiology of the shark Cretodus crassidens 15 cusplet. In two cases (nos. 2 and 35), it is triangular in outline and pointed, whereas in others it is papilla-like. In one tooth (no. 32; Fig. 10.6), one cusplet (the distal one) is smaller than the other. Besides those with additional or smaller cusplets, the sam- ple also contains malformed teeth (Fig. 10.7–10.11). Tooth number 10 has a weakly and irregularly crenulated heel on the shoulder of the main cusp instead of a well-formed cusplet (Fig. 10.7). This kind of malformation also occurs in three other teeth (nos. 52, 81, and 96). The main cusp of tooth number 47 (Fig. 10.8) is bent lingually and one cusplet is overgrown, bulky, and also recurved lingually. Tooth number 58 (Fig. 10.9) has the central cusp divided into two parts by a deep notch; the distal slice grew independently with its own apex, like a shark tooth figured by Welton and Farish (1993, fig. 17K). Furthermore, the distal cusplet is overgrown and tall. Tooth number 66 (Fig. 10.10, 10.11) has a main cusp that is partially twisted, and its apical part is blunt with a demarcated, diminutive apex. Malformed teeth also occur in other Cretodus crassidens specimens from the Chalk Group of England discussed herein. The most common malformation is the loss of lateral cusplet and replacement by a weakly, irregularly crenulated heel on the shoulder of the main cusp. This kind of malformed tooth is present in specimens with associated tooth sets, e.g., NHMUK PV OR 25786 and BMB 007312, but also in isolated teeth, namely the holotype NHMUK PV OR 25823, NHMUK PV OR 49951, and NHMUK PV P 12870. Malformed teeth have been object of several studies and reports on both fossil and living sharks. Gudger (1937) provided the probably first methodic report of malformed teeth in extant sharks. Later, some authors focused on tooth pattern reversal (Compagno, 1967; Reif, 1980), which also contributed to the development of subsequent studies on pattern formation in development of chondrichthyan dentitions from an evolutionary perspective (Smith et al., 2013). Other studies focused on Figure 13. Growth band pairs count of Cretodus crassidens (Dixon, 1850), feeding-related malformations in early growth stages (Becker MPPSA IGVR 91032. Vertebral centrum shows 23 incremental growth band pairs presumably formed annually (arrow indicates the center of the centrum; et al., 2000; Becker and Chamberlain, 2012). Tooth anomalies ‘0’ indicates vertebral size at birth). Scale bar = 50 mm. in fossil and extant sharks consist mainly of curved or twisted crowns, punctures or notches, deformed or missing cusps, fusion of teeth of the same tooth family, excessive growth of from additional complete or associated remains of closely dentine, or abnormal root morphology (Becker et al., 2000; related genera. Witzmann et al., 2021). Because damaged shark teeth cannot heal, Johnson (1987) and Welton and Farish (1993) regarded Teratologic remarks.—A certain variability in the morphological all shark tooth deformities as developmental in origin, i.e., the pattern of the cusplets that could be interpreted as malformations result of mutation or damage at an early growth stage (Wiztmann (Gudger, 1937; Becker et al., 2000) can be observed in MPPSA et al., 2021). Based on comparisons with extant sharks, Becker IGVR 91032 (Figs. 10, 11; Amalfitano et al., 2017a, fig. 6). In et al. (2000) noted that many of the observed tooth anomalies in tooth number 10, one of the shoulders of the central cusp bears extant and fossil sharks were likely from feeding-related injury to a cusplet with two further cuspules, i.e., a tricuspid cusplet the dental lamina of the jaws, particularly by impaction of chon- (Fig. 10.1). The other shoulder has a crenulated cutting edge drichthyan and teleost fin and tail spines. Furthermore, these (Fig. 10.1). In three teeth (nos. 22, 24, and 33), a papilla is authors explicitly stated that at least some malformed teeth could present on the cutting edge between the central cusp and the be caused by disease or mutation. However, the original cause of normally developed cusplet. In two cases (nos. 24 and 33; any dental anomaly could be virtually impossible to determine Fig. 10.2, 10.3), this occurs in the mesial half of the crown. A in a fossil shark (Shimada, 1997c; Wiztmann et al., 2021). small supplementary cusplet is found in three teeth (nos. 2, 7, Teeth of the sample described above are affected by several and 35; Fig. 10.4, 10.5) mesial to the mesial cusplet. In another malformations that do not differ from malformations listed tooth (no. 9), it is unclear whether the small supplementary above and reported in other sharks. Fifteen teeth out of 120 cusplet is mesial to the mesial cusplet or distal to the distal total (including those with atypical size or number of cusplets) https://doi.org/10.1017/jpa.2022.23 Published online by Cambridge University Press 16 Journal of Paleontology:1–23 exhibit malformations. Despite the incompleteness of the sam- compared to any other lamniform shark, Squalicorax Whitley, ple, the incidence of malformations in only one specimen is 1939 (Shimada and Cicimurri, 2005). Accordingly, the head rather high, if compared with other Cretaceous species numbers would also be laterally expanded. The shape of vertebral with larger datasets (e.g., from ∼0.015% in Squalicorax kaupi centra, almost perfectly circular and rostrocaudally short, is (Agassiz, 1843) to ∼0.36% in Paranomotodon sp.; Becker like many other Cretaceous lamniform sharks (e.g., et al., 2000). This difference is certainly due to a sampling Cretoxyrhina, Shimada, 1997c; Cardabiodon, Newbrey et al., bias, but the high incidence could be due to the peculiar trophic 2015; Squalicorax, Shimada and Cicimurri, 2005). Thus, it preferences of Cretodus crassidens, as evidenced by the associ- could be inferred that this shark had a fusiform body with a ation with marine turtle remains, or to the ontogenetic stage of circular girth at the trunk region, with a great vertebral column the individual. Thus, the dental malformations could be inter- elasticity that allowed carangiform swimming behavior preted as feeding-related injuries to the dental lamina (e.g., (Newbrey et al., 2015). The length of the entire semielliptical Becker et al., 2000) or as senile characters (especially the lateral dental arch, calculated with a geometric approximation cusplet loss and replacement with crenulated heel; Siversson and (Supplemental Data 2), is ∼137 cm. Using, then, this new value Machalski, 2017). applied to the relation between ‘bite circumference’ and TL by Lowry et al. (2009), the estimated TL of the individual is ∼813 Body size and body form: paleoecological remarks.—The cm. All of these estimates are more or less consistent, and it is Italian specimen MPPSA IGVR 91032 allows some reasonable to define an estimated range of TL between ∼660 suppositions on the overall morphology and size of Cretodus and ∼ 780 cm (Fig. 11), based on the vertebral centrum crassidens. The two segments preserved measure ∼244 cm diameter, which is apparently the least biased proxy. and 182 cm (although the latter was completely reworked by Another parameter useful to infer body form and paleoecol- the preparator). The sum is ∼426 cm, but many vertebral ogy of a shark is the morphology of the placoid scales (Reif, centra are missing and this could be an underestimation of the 1982, 1985; Reif and Dinkelacker, 1982), which are preserved TL of the individual. Applying the least square liner in MPPSA IGVR 91032. Amalfitano et al. (2017a) and Shimada regression method (Supplemental Data 1; r2 = 0.86115), it is and Everhart (2019) discussed the morphology of the placoid possible to estimate an original vertebral count of 169 scales to infer the swimming behavior of Cretodus. Shimada vertebral centra, similar to the vertebral count of other extant and Everhart (2019) observed, contra Amalfitano et al. and extinct large lamniform sharks (Springer and Garrick, (2017a), that the strong ridges and plications ornamenting the 1964; Shimada et al., 2006; Natanson et al., 2018). The mean placoid scale crown do not extend posteriorly on the exterior length of the vertebral centra is ∼ 32.5 ± 6.22 mm, therefore crown face, unlike those of typical fast-swimming lamniforms, the estimated articulated vertebral column is ∼549 cm long. including fossil taxa interpreted as fast pelagic-hunting sharks, Considering the intervertebral disc length (+10%; Newbrey e.g., Cretoxyrhina (Shimada, 1997b, c; Shimada et al., 2006; et al., 2015), taphonomic compression (+20%; Newbrey et al., Amalfitano et al., 2019) and Cardabiodon (Dickerson et al., 2015), and skull length (+50 cm; approximation based on the 2013; Newbrey et al., 2015). This morphological condition is Cretoxyrhina skull length, 60 cm, from Shimada, 1997c and also present in scales of the holotype of Cretodus houghtonoum Newbrey et al., 2015, and presuming a shorter and more (FHSM VP 17575; Shimada and Everhart, 2019). For this rea- laterally expanded skull in Cretodus), the estimated total son, the ridge spacing and the crown width from the original length of the Italian specimen is ∼764 cm. The body size sample of Amalfitano et al. (2017a) were measured (Appendix estimates reported by Amalfitano et al. (2017a) suggested a 3). The mean scale crown width is 562 ± 103.31 μm, whereas TL ranging 661–776 cm based on the size of the vertebral the mean ridge spacing is 87.32 ± 30.65 μm. Plotting these centra. The new estimate, based on the vertebral centrum values with those of extant sharks and Cretoxyrhina mantelli length and approximate vertebral count, falls within the Agassiz, 1835 (data retrieved from Reif, 1985, Shimada, previous estimated range. This estimate can be compared also 1997a, and Amalfitano et al., 2019; Fig. 12), the Cretodus cras- to TL estimates based on tooth size. The largest CH measured sidens value falls close to the group of large nearshore predators in the Italian specimen is ∼56 mm (Appendix 1) and if the and moderate-speed pelagic predators (sensu Reif, 1985). This CH of 56 mm is applied to the equation used by Shimada confirms the assumption made by Shimada and Everhart (2008), the calculation provides a TL of 700 cm. On the other (2019) that considers Cretodus a more sluggish swimmer with hand, the linear function from Shimada et al. (2020) provides higher maneuverability (as also evidenced by vertebral centra an estimated TL of ∼659.6 cm, which, if applied to the largest morphology) than thunniform fast-cruising swimmers, e.g., teeth of the Cretodus crassidens dentition, is very close to the Cretoxyrhina. This assumption is corroborated by association previous value of 661 cm based on vertebral centra diameter. with the turtle remains, which suggests a trophic preference of Shimada and Everhart (2019) also suggested that Cretodus Cretodus crassidens toward these reptiles, similar to that of had a stouter body than Cretoxyrhina, observing the the extant tiger shark, Galeocerdo cuvier (Péron and Lesueur arrangement of the teeth in a 120 cm wide arch (assuming that in Lesueur, 1922), which displays very similar placoid scale they are not dislodged) and the 156 cm long, 108 cm wide ornamentation combined with the ecological niche of a large elliptical accumulation of turtle bones interpreted as gastric nearshore predator (Reif, 1985). Shimada and Everhart (2019), content. These indicate a rather stout body, with an abdominal in their discussion of the ecology of the genus Cretodus, width of at least 108 cm, and a wide, gently curved, laterally reported that during excavation of the holotype of Cretodus expanded mouth aperture, almost semielliptical, more like houghtonoum (FHSM VP 17575) that remains of two additional Galeocerdo Müller and Henle, 1837 (Randall, 1992) or, species of sharks were identified from the same stratigraphic https://doi.org/10.1017/jpa.2022.23 Published online by Cambridge University Press Amalfitano et al.—Morphology and paleobiology of the shark Cretodus crassidens 17 Figure 14. Suggested growth models of Cretodus crassidens (Dixon, 1850) based on MPPSA IGVR 91032 (see text; Table 1): (1) von Bertalanffy growth function fitted to data points that show the relationship of number of vertebral growth band pairs with estimated total body length of 660 cm (TL1); (2) von Bertalanffy growth function fitted to data points that show relationship of number of vertebral growth band pairs with estimated total body length of 780 cm (TL2). Gray silhouette indi- cates the lower limit (660 cm); black silhouette indicates the upper limit (780 cm). Silhouette modified after illustration by O.E. Demuth figured by Cooper et al. (2020, fig. 2D). https://doi.org/10.1017/jpa.2022.23 Published online by Cambridge University Press 18 Journal of Paleontology:1–23 Age estimate and growth model.—One of the vertebral centra of MPPSA IGVR 91032 exhibits a total of 23 pairs of growth bands on the articular surface of the corpus calcareum (Fig. 13, Table 1). Each pair of growth bands is traditionally interpreted to have been deposited annually (Cailliet, 1990; Cailliet and Goldman, 2004), with the total band pair number (BN) indicating the age at death. Such growth band pairs do not necessarily record age or time but rather are related simply to growth or vertebral size (Harry, 2018; Natanson et al., 2018; Natanson and Deacy, 2019). Hence, the relationship of BN with time or age is loosely correlated (Natanson et al., 2018) and generally tends to retrieve an underestimation or an overestimation, because not all growth bands are necessarily consistent with aging for the entire lifespan (Passerotti et al., Figure 15. Plot of percentage increment of the vertebral radius of Cretodus 2014; Harry, 2018, Natanson et al., 2018), especially in older crassidens (Dixon, 1850) (MPPSA IGVR 91032) and Cretodus houghtonorum individuals or when later growth bands are not annual. Shimada and Everhart, 2019 (FHSM VP 17575). Arrows indicate peaks inter- preted as maturity onset for Cretodus crassidens (black) and Cretodus houghto- However, it is possible to hypothesize that the individual of norum (gray). Cretodus crassidens MPPSA IGVR 91032 was at least 23 years old at the time of its death if the deposition of each pair of growth bands is annual. The hypothetical von horizon in immediate association with FHSM VP 17575, Bertalanffy growth function (VBGF) is here reconstructed namely two teeth of Squalicorax cf. S. falcatus (Agassiz, based on the individual MPPSA IGVR 91032 and following 1843) (FHSM VP 19273 and 19274) and two partial dorsal the same estimates made by Shimada and Everhart (2019), fin spines of a hybodontid shark (FHSM VP 19272) comingled with the aim to compare the ontogenetic growth of the two with remains of Cretodus houghtonorum. This fossil association species Cretodus crassidens and Cretodus houghtonorum is interpreted as another case of a ‘vertebrate three-level (Figs. 14, 15). The VBGF is applied to the size estimates trophic chain’ (Kriwet et al., 2008, p. 183), but involving discussed above, namely ∼660 cm and ∼780 cm. The VBGF three species of sharks in this instance (Shimada and Ever- fitted to the BN-TL (660 cm) (Fig. 14.1) data gives the hart, 2019). The individual of Cretodus houghtonorum must following growth parameter estimates: L∞ (maximum TL) = have died shortly after ingesting the hybodont because of the 955.22 cm; L0 (total length at birth) = 141.9 cm; k = 0.045 yr-1; absence of acid-etching alteration on the hybodont remains; estimated longevity (after Natanson et al., 2006) = 64.429 yr. the Cretodus houghtonorum carcass was scavenged by S. cf. The BN-TL (780 cm) data (Fig. 14.2), on the other hand, S. falcatus before or during the decay, followed by retrieve the following parameters: L∞ = 1128.8 cm; L0 = 167.7 cm. disarticulation and scattering of the skeletal and dental elements The longevity estimate of ∼64 yr is consistent with those for of Cretodus houghtonorum due to the presence of weak water extant large lamniform sharks (Camhi et al., 2008) and that of currents on the seafloor (Shimada and Everhart, 2019). Cretodus houghtonorum (∼55 years; Shimada and Everhart, Hybodont remains are more common in shallow-nearshore 2019). environments, if not in fresh or brackish water environments The percentage increment of the centrum radius of Creto- (e.g., Underwood and Rees, 2002; Underwood, 2004; Sweet- dus crassidens and Cretodus houghtonorum was also consid- man and Underwood, 2006), and the presumed predator-prey ered to find any significant variation in growth rate and for relationship between Cretodus houghtonorum and the further comparison (Fig. 15). The percentage increment of the hybodontid shark suggests that Cretodus houghtonorum dwelled, two species is almost identical, except for two delayed peaks, at least sometimes, in shallow-nearshore environments. This which could correspond to the maturity onset at 12–17 years assumption is supported by the fact that although Cretodus and 10–15 years, respectively. The maturity onset is consistent houghtonorum and Cretoxyrhina mantelli lived contemporan- with those of other large macropredatory lamniform sharks eously (Shimada, 2006), the distribution of the two taxa (Camhi et al., 2008). The delayed growth peaks could alterna- indicates that they likely practiced resource partitioning within tively be caused by sexual dimorphism, with females maturing the North American Western Interior Sea, because Cretodus later than males (Camhi et al., 2008). However, despite the houghtonorum teeth are more commonly found in nearshore strong similarities between the two species, there is no evidence deposits whereas those of Cretoxyrhina mantelli are common in to support Cretodus crassidens and Cretodus houghtonorum offshore deposits (Shimada and Everhart, 2019). The occurrence dentitions as gynandric heterodont variants, but rather they of Cretodus crassidens in the pelagic deposits of the Scaglia were vicariant species dwelling in different environments (Cre- Rossa and Chalk Group, however, implies that this species pref- todus crassidens in offshore settings, Cretodus houghtonorum erentially dwelled in the offshore setting. It must be remarked, in nearshore settings) or geographically separated (Cretodus however, that Cretodus crassidens is represented by a single spe- crassidens in the European Tethys and Boreal seas, Cretodus cimen in the Scaglia Rossa to date, whereas Cretoxyrhina mantelli houghtonorum in the Western Interior Seaway; see also Guinot and Ptychodus spp. remains are much more common (Amadori and Cavin, 2016 for vicariances related to the Cenomanian et al., 2019, 2020a, b; Amalfitano et al., 2019). diversification event). After attaining maturity, the growth rate https://doi.org/10.1017/jpa.2022.23 Published online by Cambridge University Press Amalfitano et al.—Morphology and paleobiology of the shark Cretodus crassidens 19 in the plot generally tends to become asymptotic, as evidenced Acknowledgments after the peaks at 17 and 15 yr, respectively. The growth model provided herein allows calculation of the R. Zorzin (Museo Civico di Storia Naturale di Verona), possible TL of other specimens. The growth bands are not well E. Bernard (NHMUK), and L. Ismail and J. Cooper (BMB) preserved on the two vertebral centra of BMB 007312. The spe- are deeply thanked for access to the specimens and to in- cimen also includes the lower second anterior tooth, the CH of formation about the collections under their care. Copyright of which measures 47 mm (Appendix B). If the linear functions the NHMUK photos is reserved by K. Webb and The Natural CH-TL extrapolated from MPPSA IGVR 91032 is applied, i.e., History Museum (NHMUK). S. Castelli (Dipartimento di Geos- cienze, Università degli Studi di Padova) is also acknowledged for their valuable contribution with photos and postproduction TL1 (cm) = 11.78 × CH(mm) + 0.24 (4) for the Italian material. Funding for this research was provided by University of Padova (Progetto di Ateneo CPDA159701/ 2015, titled ‘Reappraisal of two key Fossil-Lagerstätten in Sca- glia deposits of northeastern Italy in the context of Late Cret- TL2 (cm) = 13.92 × CH(mm) + 0.29 (5) aceous climatic variability: a multidisciplinary approach,’ assigned to E. Fornaciari and Dotazione Ordinaria Ricerca (DOR) funds assigned to L. Giusberti). The reviewers the estimated TL of BMB 007312 results in a range between M. Siversson, C. Underwood, and D.J. Ward, and the Editor ∼554 cm and ∼654 cm (versus an estimated TL range of 546– H.-D. Sues are deeply thanked for helpful and valuable sugges- 573 cm when applying the equations used by Amalfitano et al. tions on an earlier draft of this paper. [2017a] based on vertebral centrum diameter). The age at death was ∼16–17 years if the CH is considered, comparing Data availability statement this specimen to MPPSA IGVR 91032 (Table 1). Data available from the Dryad Digital Repository: https://doi. Conclusions org/10.5061/dryad.31zcrjdnk. The specimen MPPSA IGVR 91032 and others described herein References provide new morphological and paleobiological information about the Late Cretaceous large-sized shark genus Cretodus. Adnet, S., 2006, Biometric analysis of the teeth of fossil and Recent hexanchid The specimen is assigned to Cretodus crassidens and recon- sharks and its taxonomic implications: Acta Palaeontologica Polonica, v. 51, no. 3, p. 477–488. struction of its dentition based on the Italian specimen reveals Agassiz, L.J.R., 1835, Rapport sur les Poissons Fossiles Découverts Depuis la the peculiarities of this species with respect to other species of Publication de la Troisième Livraison, Feuilleton Additionel sur les the genus. Cretodus crassidens likely represents a separate lin- Recherches sur les Poissons Fossiles, 4th Livraison: Neuchâtel, Switzerland, Petitpierre et Prince, p. 39–64. eage within Cretodus (see the phylogenetic hypothesis by Shi- Agassiz, L.J.R., 1838, Recherches sur les Poisons Fossiles, 11th Livraison: mada and Everhart, 2019). The body form and size estimates Neuchâtel, Switzerland, Petitpierre et Prince (text) and H. Nicolet (plates), are indicative of a large-sized macropredatory shark, reaching v. 2, pls. 42, 43; v. 3, p. [73]–140, pls. 1a, 8a, 8b, 15, 17, 19, 20, 24, 25b, 30– 35, 39, 40; v. 5, pl. 60; Feuilleton Additionnel, p. 107–116. a size over the limit that defines gigantic elasmobranch species Agassiz, L.J.R., 1843, Recherches sur les Poissons Fossiles, 15th and 16th Liv- (> 6 m; Pimiento et al., 2019). The maximum estimated total raisons: Soleure, Switzerland, Jent and Gassmann (text), and Neuchâtel, length (9–11 m) and length at birth are comparable to those of Switzerland, H. Nicolet (planches), v. 2, pt. 2, p. [1]–72, pls. B’, B’’, Ca, G, 23b, 23c, 31, 33a, 36–38, 42a, 44; v. 3, p. 157–390, 382*–382**, 1– the giant Cenozoic genus Otodus Agassiz, 1838 (Shimada 32, [33]–[34], pls. 1, 18, 22, 22a, 22b, 26a, 38, 40b–40d, 45, 47; vol. 4, et al., 2021). Cretodus crassidens was probably characterized pl. 23b; vol. 5, pt. 2, p. 57–84, pls. B, C, E, H, J, K, 9, 10, 28, 29, 37b, by a moderate-speed swimming behavior, suggested by the 44–48; Feuilleton Additionnel, p. 139–144. Amadori, M., Amalfitano, J., Giusberti, L., Fornaciari, E., Luciani, V., Carne- morphology of the vertebral centra and the placoid scales. vale, G., and Kriwet, J., 2019, First associated tooth set of a high-cusped This shark was a large predator feeding on, among others, Ptychodus (Chondrichthyes, Elasmobranchii) from the Upper Cretaceous large protostegid turtles, as evidenced by the gastric content pre- of northeastern Italy, and resurrection of Ptychodus altior Agassiz, 1835: Cretaceous Research, v. 93, p. 330–345, https://doi.org/10.1016/j.cretres. served within the individual from the basinal high settings of the 2018.10.002. ‘Lastame.’ Estimated age at death (23 yr) and longevity (64 yr) Amadori, M., Amalfitano, J., Giusberti, L., Fornaciari, E., Carnevale, G., and Kriwet, J., 2020a, The Italian record of the Cretaceous shark, Ptychodus are consistent with those of extant large lamniform shark popu- latissimus Agassiz, 1835 (Chondrichthyes; Elasmobranchii): PeerJ, v. 8, lations not subject to anthropic pressure. Interestingly, this study p. e10167, https://doi.org/10.7717/peerj.10167. notes that Cretodus crassidens fossils occur both in Boreal and Amadori, M., Amalfitano, J., Giusberti, L., Fornaciari, E., Carnevale, G., and Kriwet, J., 2020b, A revision of the Upper Cretaceous shark Ptychodus Tethyan domains at the same interval, implying a broad paleo- mediterraneus Canavari, 1916 from northeastern Italy, with a reassessment biogeographic distribution. Moreover, Cretodus crassidens of P. latissimus and P. polygyrus Agassiz, 1835 (Chondrichthyes; Elasmo- exhibits a likely preference toward offshore settings, in contrast branchii): Cretaceous Research, v. 110, p. 104386, https://doi.org/10.1016/j. cretres.2020.104386. with other species of the genus found in nearshore settings, indi- Amalfitano, J., Dalla Vecchia, F.M., Giusberti, L., Fornaciari, E., Luciani, V., cating a possible vicariance scenario. 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Placoid scale measurements of Cretodus crassidens (Dixon, 1850). mm). The numbers of teeth are those reported by Amalfitano et al. (2017a, fig. 6). CH = crown height; CT = crown thickness (labiolingual); CW = crown width; Scale Scale width Ridge spacing (μm) DCL = distal cutting-edge length; LCH = cusplet height; MCL = mesial Sample location (μm) cutting-edge length; PCH = central cusp height; PCW = central cusp width; TH IGVR 91032 unknown 88-123-162 433 = tooth height; TT = tooth thickness (labiolingual); TW = tooth width. 99-113-92 711 Gray-shaded cells are those corrected. 78-83-93-58-60-89 548 82-138-105-137-86-76 694 Tooth TH TW TT CH CW CT LCH PCH PCW MCL DCL 49-50-46-76-116-88-49-74-65-25 497 3 69 52 22 56 46 16 16 39 27 42 41 115-115-81-59 600 6 41 - 21 33 - 10 - 24 17 - - 69-130 451 16 48 36 10 34 25 6 11 22 14 26 24 mean (n = 7) 87.32 ± 30.65 562 ± 103.31 Appendix 2. Tooth measurements of BMB 007312 (in mm). The table includes measurements of some of the best-preserved teeth. CH = crown height; CT = crown thickness (labiolingual); CW = crown width; DCL = distal cutting-edge length; LCH = cusplet height; MCL = mesial cutting-edge length; PCH = central cusp height; PCW = central cusp width; TH = tooth height; TT = tooth thickness (labiolingual); TW = tooth width; * = tooth isolated from the matrix. Tooth TH TW TT CH CW CT LCH PCH PCW MCL DCL a2 51 36 20 47 33 11 8 38 22 50 49 l2?* - - - - - 12 - 29 19 - - a1 - - - - - 11 - 38 22 - - L1? - - - 26 19+ 6 4 18 14 - 25 L8? 19? - - 16 20? - 4 13 10 16 https://doi.org/10.1017/jpa.2022.23 Published online by Cambridge University Press