Drumheller and Brochu | 1

1 PHYLOGENETIC TAPHONOMY: A STATISTICAL AND PHYLOGENETIC

2 APPROACH FOR EXPLORING TAPHONOMIC PATTERNS IN THE FOSSIL

3 RECORD USING CROCODYLIANS

4 STEPHANIE K. DRUMHELLER1, CHRISTOPHER A. BROCHU2

5 1. Department of Earth and Planetary Sciences, The University of Tennessee, Knoxville,

6 Tennessee, 37996, U.S.A.

7 2. Department of Earth and Environmental Sciences, The University of Iowa, Iowa City, Iowa,

8 52242, U.S.A.

9 email: [email protected]

10 RRH: CROCODYLIAN BITE MARKS IN PHYLOGENETIC CONTEXT

11 LRH: DRUMHELLER AND BROCHU Drumheller and Brochu | 2

12 ABSTRACT

13 Actualistic observations form the basis of many taphonomic studies in paleontology.

14However, surveys limited by environment or taxon may not be applicable far beyond the bounds

15of the initial observations. Even when multiple studies exploring the potential variety within a

16taphonomic process exist, quantitative methods for comparing these datasets in order to identify

17larger scale patterns have been understudied. This research uses modern bite marks collected

18from 21 of the 23 generally recognized species of extant Crocodylia to explore statistical and

19phylogenetic methods of synthesizing taphonomic datasets. Bite marks were identified, and

20specimens were then coded for presence or absence of different mark morphotypes. Attempts to

21find statistical correlation between trace types, marking animal vital statistics, and sample

22collection protocol were unsuccessful. Mapping bite mark character states on a eusuchian

23phylogeny successfully predicted the presence of known diagnostic, bisected marks in extinct

24taxa. Predictions for clades that may have created multiple subscores, striated marks, and

25extensive crushing were also generated. Inclusion of fossil bite marks which have been positively

26associated with extinct species allow this method to be projected beyond the crown group. The

27results of this study indicate that phylogenies can and should be further explored for use as

28predictive tools in a taphonomic framework.

29 INTRODUCTION

30 Bite marks represent direct evidence of diet, feeding behavior (e.g., Davidson and

31Soloman 1990; Forrest 2003; Fuentes 2003), and even inter- or intraspecific fighting (e.g.,

32Buffetaut 1983; Williamson 1996; Avilla et al. 2004; Katsura 2004) in the fossil record. These

33bone surface modifications exist at an intersection of ichnology and taphonomy, in which tooth

34shape and structure, jaw morphology and mechanics, and behavior act in concert to create Drumheller and Brochu | 3

35patterns of modification, accumulation, and destruction of remains. Patterns of modern bite

36marks are often observed in order to identify novel traces that could be used for identification

37and interpretation of similar structures in the fossil record (e.g., Njau and Blumenschine 2006;

38Milan et al. 2010; Westaway et al. 2011; Baquedano et al. 2012; Drumheller and Brochu 2014).

39However, sampling of modern bite marks has been uneven across and within clades, and many

40studies focus on a small number of modern groups, sometimes even a single species, to make

41predictions about diverse, extinct clades or morphologies. Drawing such broad conclusions based

42on analyses with strongly restricted study parameters may well be masking patterns of natural

43variation (Lyman, 1994; Haglund and Sorg, 1997).

44 For example, domestic dogs (Canis familiaris) and wolves (e.g., Canis lupus, Canis

45rufus) have an extensive bite mark literature (e.g., Binford 1981; Haynes 1982; Haglund 1997a)

46reflecting their common interaction with forensic sites, importance to studies of early

47domestication, and habit of caching and heavily modifying bones. Among mammals, hyenas

48(e.g., Haynes 1983; Cruz-Uribe 1991; Marean and Spencer 1991), great cats (e.g., Brain 1981;

49Haynes 1983; Domínguez-Rodrigo 1999), bears (e.g., Haynes 1982; Domínguez-Rodrigo and

50Piqueras 2003), and rodents (e.g., Brain 1981; Haglund 1997b; Klippel and Synstelien 2007)

51have also received a substantial amount of attention from bite mark researchers. At the other end

52of the spectrum, bite marks from only one squamate, the Komodo dragon (Varanus

53komodoensis), have been systematically studied, and this dataset stands as the sole modern

54datapoint for comparison with a diversity of ziphodont predators (D’Amore and Blumenschine

552009).

56 When multiple surveys within a clade do exist, it is unclear how the results should be

57synthesized, introducing a large degree of uncertainty into interpretations of ancient bite marks Drumheller and Brochu | 4

58based on comparisons to modern ones. Moreover, differing collection protocols and research

59methodologies can hinder statistical comparisons between these datasets. Researchers frequently

60fall back on simply comparing and contrasting their results (Haynes 1983; Drumheller and

61Brochu 2014). However, if a uniform collection protocol could be applied across multiple

62groups, more rigorous ways to explore patterns across the sampled taxa would become available.

63 Here, we present the results of an actualistic survey of bite marks collected from 21

64species of extant Crocodylia. Recent studies have expanded our existing knowledge of the bone

65surface modifications this clade can generate, including potentially diagnostic traces (Njau and

66Blumenschine 2006; Milan et al. 2010; Westaway et al. 2011; Baquedano et al. 2012;

67Drumheller and Brochu 2014). The fossil record of bite marks generated by crocodylians and

68their more distant relatives also has garnered increased attention and study (Davidson and

69Soloman 1990; Carpenter and Lindsey 1980; Erickson 1984; Schwimmer 2002, 2010; Forrest

702003; Fuentes 2003; Cisneros 2005; Mikulás et al. 2006; Martin 2013). In addition to serving as

71important predators and taphonomic agents in their own rights (Noto et al. 2012; Boyd et al.

722013), crocodylians are popular proxies for several extinct clades, including a variety of other

73archosaur-line reptiles (Brazaitis and Watanabe 2011; Drumheller et al. 2014). Therefore a better

74understanding of their feeding behaviors and resulting traces has broad potential for application

75to a large number of paleoecological and paleobiological questions.

76 We further explore patterns of feeding trace expression across this collection of

77crocodylian bite marks with associated metadata representing details characterizing each animal

78and collection methodology used during specimen collection. This allows statistical tests of

79significance between presence or absence of mark types and variables such as age, sex, specimen

80type, and collection protocol. The possibility that phylogeny could inform taphonomic patterns is Drumheller and Brochu | 5

81explored by applying a modified version of the extant phylogenetic bracket method (Witmer

821995). This study will serve not only as a survey of bite marks expected among crocodylians and

83their more distant relatives, but also as a case study demonstrating how future datasets

84addressing a variety of taphonomic and behavioral questions might be collected and synthesized.

85 MATERIALS AND METHODS

86 Bite Mark Collection and Preparation

87 Partially butchered cow hind limbs and pig femora were obtained from meat packaging

88plants and transported to the St. Augustine Alligator Farm (SAAF) in St. Augustine, Florida.

89Cow specimens retained significant amounts of flesh at the joints, and included articulated

90femora, tibiae, patellae, and varying numbers of tarsals depending on how much of the foot was

91removed during the butchering processes. Pig femora experienced more initial processing and

92were largely defleshed.

93 Bite marks were collected from 65 individuals, representing juveniles to very large

94adults, from 21 of the 23 generally recognized extant crocodylian species, excluding Gavialis

95gangeticus and Crocodylus palustris (Supplementary Table 1). Bite marks were collected from

96isolated individuals, so that veterinary data kept by SAAF staff could be correlated to specific

97samples (Fig. 1). Smaller animals were presented with isolated pig femora, and larger animals

98were given partially butchered cow hind limbs. Samples usually were collected once voluntarily

99abandoned, although some animals had to be distracted by handlers to prompt sample

100abandonment once active biting ceased. Animals were unrestrained while bite mark samples

101were collected, except when the SAAF staff felt that handler and animal safety was a concern. In

102those cases, often related to the small size relative to bone samples or the aggressive nature of the

103individuals, animals were held near the base of the skull by a handler or, with larger animals, Drumheller and Brochu | 6

104secured by the handler sitting on the back of the animal. Specific feeding behaviors, such as axial

105rolling or violent lateral thrashing, were recorded. Collection protocol and vital statistics (sex,

106mass, age, total length, snout-vent length, cranial length, and whether each animals was born in

107captivity or in the wild, restrained or free during specimen collection, and whether presented

108with cow limbs or pig femora) were recorded for each animal and are presented in

109Supplementary Table 1.

110 After collection, samples were defleshed and degreased via simmering in water with

111Borax®, an enzymatic detergent. After rinsing and manual removal of any remaining soft tissue,

112bones were cleaned again with Luminox® and Dawn®, milder, non-enzymatic detergents.

113Sponges and soft plastic brushes were used to prevent further bone surface modifications during

114the cleaning process. Enzymatic detergents have proven to be highly successful at cleaning bone

115when long-term curation is not an end goal (e.g., Fenton et. al. 2003; Mairs and Rutty 2004;

116Steadman et. al. 2006). Since these samples were destined for further destructive preparation,

117efforts to prevent continued, long-term digestion of the bone by the active enzymes were not

118made (Shelton and Buckley 1990).

119 Bite Mark Identification and Classification

120 Bite marks, as well as butchering traces, were identified using the criteria described by

121Blumenschine et al. (1996). Classification was modeled after Binford (1981) wherein all marks

122are separated into four broad groupings: pits, punctures, scores, and furrows. Pits represent

123depressions on the surface of a bone caused when a tooth tip indents, but does not fully pierce,

124the cortical bone. When piercing does occur, the mark is instead classified as a puncture. When

125the tip of the tooth drags along the surface of the bone, leaving a crushed groove that does not

126fully pierce the cortical bone, the mark is called a score. When a similar bite does pierce the Drumheller and Brochu | 7

127cortical bone, the mark is classified as a furrow (Fig. 2).

128 These broad categories of bite marks can be further divided by any novel mark

129morphology or pattern of expression. In the case of crocodylians, Njau and Blumenschine (2006)

130identified two new types of bite marks in their diagnosis of Crocodylus niloticus feeding traces:

131bisected marks and hook scores. Bisected marks were pits, punctures, and scores (furrows were

132not identified in this study) that exhibited subscoring and/or notching on bite margins. These

133structures were formed by the prominent carinae present on relatively unworn, recently erupted

134crocodylian teeth. Hook scores were defined as J- or L-shaped marks, created when the trajectory

135of a single tooth abruptly changed directions during a biting event. Such marks were tentatively

136associated with death rolling behavior. Hook scores were later identified among modern

137Komodo dragons (Varanis komodoensis) and non-avian theropods (D’Amore and Blumenschine

1382009), suggesting they are not diagnostic of crocodylians or death rolling. Bisected marks,

139however, appear unique to crocodylians and non-crocodylian crocodyliforms (Drumheller 2007;

140Rivera-Sylva et al. 2009; Brochu et al. 2010; Noto et al. 2012; Boyd et al. 2013; Botfalvai et al.,

1412014; Drumheller and Brochu 2014).

142 Secondary alterations related to impact trauma, such as depressed fractures, which occur

143when the margins of a bite mark collapse irregularly under the force of the impacting tooth, can

144also occur. Bone may also fracture radially away from the location of the impact, a secondary

145alteration called fracture lines. Spiral or green stick fractures occur when a bite is powerful

146enough to completely break the bone; these fractures typically propagate in a spiral fashion

147around the circumference of long bones (Byers 2005; Wescott 2013). It should be noted that such

148alterations can be associated with any kind of impact trauma, and are not unique to biting events.

149 Bite marks were photographed in detail with an Olympus® Stylus™ 760 still-image Drumheller and Brochu | 8

150camera. Blind inter-analyst tests have shown that bite marks can be differentiated from other

151types of bone surface modifications using only a 10X hand lens for magnification (Blumenschine

152et al. 1996). However, the presence or absence of bisected marks has been specifically related to

153the relative wear and chipping of the carinae of teeth, with different tooth morphologies and

154levels of wear present within the mouth of a single individual (Njau and Blumenschine 2006).

155Therefore, observing marks under higher magnification could reveal more subtle bisections

156caused by incompletely worn carinae. After light photography, specimens were sectioned into

157pieces (<10 cm maximum length) and imaged on a Hitachi® S-3400N variable pressure

158scanning electron microscope (VP-SEM).

159 Statistical Analyses of Vital Variables and Collection Protocols

160 Once identified, correlation between the presence or absence of novel types of bite marks

161(i.e., subscores) and vital statistics of the animals and collection protocols was tested using either

162a one-way ANOVA (Fisher, 1925) or a chi-squared test of independence (Pearson, 1900). The

163ANOVA works from the null hypothesis that samples from the tested groups (mark type

164presence vs. absence) were drawn from the same underlying population, and is appropriate for

165analyses involving continuous, measured variables (i.e., age, total length, head length, snout-vent

166length, and mass), assuming that sampling is random, variables are independent, and population

167variances are equal. This is a parametric test, and while it is robust to violations of the

168assumption that the tested variables are normally distributed when sample sizes are large, further,

169nonparametric testing, in the form of a Kruskal-Wallis one-way analysis of variance (Kruskal-

170Wallis 1952), was performed as well. The chi-squared test of independence (also called

171Pearson’s chi-squared test) is used to assess whether binary, categorical variables (i.e., sampled

172bone type, collection protocol, sex, origin, and snout ectomorph tested against mark Drumheller and Brochu | 9

173presence/absence) are independent of one another, assuming random sampling, variable

174independence, and a large sample size (these data are near the lower bound). These tests were

175performed with the PAST statistical software package (Hammer et al. 2001), along with that

176software’s standard assumption tests, including Levene’s (1960) and Shapiro-Wilk (1965), and

177were used to determine whether these variables might be affecting the observed patterns of bite

178marks. All data used in these analyses are presented in Supplementary Table 1.

179 Phylogenetic Analysis and Character Mapping

180 Bite mark morphology represents a combination of morphological and behavioral traits

181and may retain a phylogenetic signal. Dental characters, while often highly conserved across

182major crocodylian clades, do retain a phylogenetic signal (Brochu et al., 2012; Brochu, 2013). It

183is unclear how hybrid behavioral and morphological characters, such as bite marks, may be used

184in phylogenetic analyses, because behavioral traits are inherently more labile than morphological

185or molecular characters and, in principle, are secondary expressions of underlying morphology

186and ecology. Moreover, whether learned behavior can be treated as a heritable feature subject to

187homology assessment is an open question (e.g., Wenzel, 1992; de Quieroz and Wimberger 1993;

188Blomberg et al. 2003).

189 However, in at least some cases behavioral characters exhibit analytical rates of

190homoplasy not statistically different from those generated from morphological datasets (de

191Quieroz and Wimberger 1993), and metrics that measure phylogenetic signal have found utility

192even in demonstrably labile behavioral datasets (Blomberg et al. 2003). Whether used as prima

193facie evidence in phylogenetic inference or not, various methods, including parsimony

194optimization, have been applied to study the evolution of behavioral characters in a phylogenetic

195context (e.g., Tullberg et al., 2002; Agnarsson et al, 2006; Paterson et al., 2014; Odom et al., Drumheller and Brochu | 10

1962015). One such method, the extant phylogenetic bracket (Witmer, 1995), is especially useful

197when fossil taxa for which soft-tissue, physiological, life-history, and behavioral features are

198generally not directly preserved. If we assume that such features shared by living species were

199inherited from their last common ancestor, we would predict their presence in extinct members

200of the group descended from that ancestor. In this specific case, bite mark expression as a

201reflection of tooth morphology can be viewed as a Type I inference (i.e., rooted in the presence

202of a preserved osteological correlate), while mark morphology as it relates to behavior is Type II

203(i.e., directly observed in extant sister taxa, but not the outgroup), using the confidence hierarchy

204established for the extant phylogenetic bracket (Witmer, 1995).

205 In order to explore whether phylogeny might be useful when synthesizing bite mark

206datasets, single (bisections) and multiple (trisections or quadrisections) subscores within

207individual bite marks from extant taxa were coded as binary characters (i.e., presence/absence)

208and mapped onto an existing eusuchian phylogeny. The tree used in this analysis was assembled

209from previous maximum parsimony analyses using matrices based on 189 morphological

210characters. Relationships within Crocodyloidea are based on Brochu and Storrs (2012).

211Relationships within other crocodylian clades are based on Brochu et al. (2012) and Brochu

212(2013), and relationships among non-crocodylian eusuchians are based on Narváez et al.

213(2015). Although they used slightly different taxon samples, relationships supported by all of

214these analyses are consistent with each other. Clades supported by one of the trees were added

215manually to the other. The complete consensus tree, with all 124 ingroup taxa, is available in the

216Supplementary Materials as Figure 1.

217 Character state changes for the bite mark characters, as well as other dental characters of

218interest from the original matrix, were mapped onto the strict consensus tree in Mesquite 2.75 Drumheller and Brochu | 11

219(Maddison and Maddison 2011) using the parsimony parameter. Patterns of unambiguous bite

220mark character state changes are interpreted to be phylogenetic predictions of presence or

221absence in the fossil record. Areas of the tree where character states were determined to be

222ambiguous by the parsimony analysis are considered to predict an equal possibility of mark

223presence or absence in the fossil record. These predictions provide a conservative estimate of

224bite mark character distribution within Eusuchia, and we test their accuracy by comparing the

225character states suggested by the extant taxa in the parsimony analysis to published examples of

226crocodylian bite marks ascribed to extinct species.

227 RESULTS

228 Bite Mark Identification and Classification

229 Presence or absence of particular bite mark types within each sampled taxon is reported

230in Table 1. Scores are present in every sampled taxon, and pits are identified in all but two,

231Paleosuchus palpebrosus and Paleosuchus trigonatus. Punctures were less common, and were

232most often correlated with the physically largest animals sampled (Alligator mississippiensis,

233Crocodylus acutus, Crocodylus porosus, Tomistoma schlegelii). One particularly aggressive, but

234smaller, male A. sinensis (SAAF 86052) deviated from this generalization, and created definite

235punctures on the pig femur presented to him. Punctures were not found in specimens collected

236from Crocodylus niloticus in this survey, but a previous study reported punctures created by

237members of the species (Njau and Blumenschine 2006). Furrows were identified, if only in two

238taxa: Alligator mississippiensis and Crocodylus novaeguineae. As with the punctures, this type

239of mark was caused by particularly large, aggressive animals. Both punctures and furrows were

240most often present at the proximal or distal ends of long bone elements, where the bone itself is

241structurally less dense. While frequency and distribution of these mark types have been used to Drumheller and Brochu | 12

242differentiate groups in larger scale studies of individual species (e.g., Drumheller and Brochu

2432014; Njau and Blumenschine 2006), these marks have been found across multiple vertebrate

244groups (Binford 1981) and therefore, in isolation, are not considered diagnostic of crocodylians.

245 Bisected marks were identified in all but seven taxa: Caiman latirostris, Mecistops

246cataphractus, Crocodylus intermedius, Crocodylus porosus, Crocodylus siamensis, Osteolaemus

247tetraspis, and Paleosuchus palpebrosus (Fig. 3). However, a previous survey of Crocodylus

248porosus bite marks tentatively reported at least one bisected mark (Westaway et al. 2011). A

249larger scale study of Crocodylus niloticus found that bisected marks represent 10% of marks

250occurring on 82.5% of all marked bones (Njau and Blumenschine 2006), with similar

251percentages being recorded in Alligator mississippiensis as well (Drumheller and Brochu 2014).

252Without a broader survey of the clade to determine regularity of bisected marks, the presence or

253absence of bisections in Crocodylus porosus is considered to be ambiguous for this study.

254 Multiple subscores were present in a smaller number of taxa, and were only identifiable

255under higher magnification. Two subscores, forming a trisection, were identified in Caiman

256yacare and Tomistoma schlegelii. Three subscores, forming a quadrisection, were found in

257Alligator sinensis, Crocodylus johnsoni, Crocodylus novaeguineae, and Osteolaemus tetraspis

258(Fig. 3).

259 Crushing associated with the biting event was visible under a hand lens, but distinctly

260obvious under the VP-SEM. Further secondary alterations – depressed fractures, fracture lines,

261and spiral fractures (sensu Byers 2005; Wescott 2013) – were most often associated with high-

262force structures such as punctures on long bone shafts. Spiral fractures were only present in

263samples taken from Alligator mississippiensis (Fig. 4), but bone breakage, often related to limb

264loss, has been reported in forensic case studies involving Alligator mississippiensis, Crocodylus Drumheller and Brochu | 13

265acutus, Crocodylus niloticus, and Crocodylus porosus (Harding and Wolf 2006; Wood 2008;

266Sartain and Steele 2009; Mendieta and Duarte 2009; Cupal-Magaña et al. 2010; Chattopadhyay

267et al. 2013). Spiral fractures previously have been reported in samples taken from a survey of

268Crocodylus niloticus (Njau and Blumenschine 2006) and in forensic case studies involving

269Crocodylus acutus (Cupal-Magaña et al. 2010) and Crocodylus porosus (Wood 2008;

270Chattopadhyay et al. 2013). All fractures found in this study had pits or punctures associated

271with the margins of the break.

272 One unusual mark was found on a sample taken from C. novaeguineae: an irregular

273series of closely spaced scores. The marks were shallower, and more V-shaped in cross section

274than normal bite marks. The animal from which this sample was collected broke a tooth during

275bite mark collection, suggesting that this mark may reflect the jagged edges of a recently snapped

276tooth crown (Fig. 4D).

277 Statistical Analyses of Vital Statistics and Collection Protocols

278 None of the recorded variables associated with animal vital statistics or collection

279protocols were found to correlate significantly with the presence or absence of novel, diagnostic

280traces (i.e., subscores). Numbers of observed subscores were not tested separately, because

281multiple subscores were extremely rare (two individuals left trisections, four left quadrisections),

282and it is probable that they represent marks left by pathological teeth (see discussion below). The

283detailed results of these analyses are presented in Table 2.

284 Phylogenetic Analysis and Character Mapping

285 Within Crocodyloidea, the presence or absence of bisected marks was found to be

286ambiguous in ten fossil taxa – Crocodylus megarhinus, Crocodylus gariepensis, Australosuchus

287clarkae, Kambara implexidens, Trilophosuchus rackhami, Quinkana spp, Rimasuchus lloydi, Drumheller and Brochu | 14

288Euthecodon arambourgii, Euthecodon brumpti, Brochuchus pigotti, Voay robustus – and modern

289Osteolaemus osborni. All remaining fossil taxa are unambiguously predicted to have been

290capable of creating bisected marks, though the absence of samples from Gavialis gangeticus

291does limit the confidence placed on predictions made regarding more basal members of the

292crown group, as they fall outside of the bracketed taxa (Fig. 5).

293 Multiple subscores were predicted to be unambiguously absent across the majority of the

294tree, except within Osteolaeminae and Tomistominae. Tomistoma schlegelii and Osteolaemus

295tetraspis did create multiple subscores in the modern survey. Within Tomistominae, the

296following thirteen fossil species were found to be ambiguous with regards to this character state:

297Tomistoma lusitanica, Toyotamaphimeia machikanensis, Gavialosuchus eggenburgensis,

298Tomistoma petrolica, Paratomistoma courti, Penghusuchus pani, Thecachampsa americana,

299Thecachampsa antiqua, Thecachampsa carolinense, Tomistoma cairense, Megadontosuchus

300arduini, Dollosuchoides densmorei, and Kentisuchus spenceri. Among the osteolaemines,

301Osteolaemus osborni and Voay robustus were also found to be ambiguous (Fig. 6).

302 Other character states mapped in order to explore potential bite mark types included

303features related to feeding strategies and tooth morphologies no longer exhibited by extant

304crocodylians. For example, Quinkana and all members of Planocraniidae have laterally

305compressed teeth (Brochu and Storrs 2012; Brochu et al. 2012; Brochu 2013), with Quinkana

306and Boverisuchus further exhibiting serrated dentition (Brochu and Storrs 2012; Brochu et al.

3072012; Brochu 2013), and therefore, true ziphodonty (Fig. 7). The members of these clades would

308therefore be expected to create marks more similar to those made by other ziphodont groups,

309such as varanids and theropod dinosaurs (D’Amore and Blumenschine 2009).

310 Members of Hylaeochampsidae, excluding Acynodon iberoccitanus, exhibit teeth that Drumheller and Brochu | 15

311increase in diameter posteriorly in the tooth row (Brochu and Storrs 2012; Brochu et al. 2012),

312including some species that have extreme expansion of their penultimate teeth into the ‘anvil’

313shape often associated with durophagy. This distinctive tooth morphology is also seen in many

314basal members of Globidonta, again interpreted to represent a durophagous feeding strategy (Fig.

3157). Although modern, generalist crocodylians sometimes exhibit durophagous behavior (Milàn et

316al. 2010), none has the expanded dentition of a true durophagy specialist. As such, beyond the

317predicted increase in secondary (i.e., crushing) damage to prey items, modern crocodylians

318possibly do not provide the best analogues for predicting the morphology of bite marks made by

319members of this clade.

320 DISCUSSION

321 Crocodylian and non-crocodylian crocodyliform bite marks long have been reported in

322the fossil record, and some recent publications discussed the presence or absence of the bisected

323marks. The patterns of bite marks reported here provide methods to predict expected traces in the

324fossil record. The results of the statistical analyses indicate that none of the recorded vital

325statistics or collection protocols correlate significantly with the expression of subscores (Table

3262). These results were somewhat surprising. Both ontogeny (e.g., McIlhenny, 1935; Erickson et

327al., 2014) and snout shape (e.g., Brochu, 2001; McHenry et al., 2006; Pierce et al., 2008; 2009)

328have been correlated with different tooth shapes and feeding ecologies, and yet analyses

329examining the relationships of associated features (i.e., age, lengths, body mass, ecomorph) to

330bisection presence or absence did not show any significant relationships. Captivity is known to

331trigger ecophenotypic change in crocodylians, particularly within the snout and tooth row (e.g.,

332Erickson et al., 2003; Sadleir, 2009; Drumheller et al., 2016), but again, whether these animals

333were wild caught or captive bred did not result in a significant difference between groups. Sexual Drumheller and Brochu | 16

334dimorphism is known in the clade (e.g., Hall and Portier, 1994; Verdade, 2003; Platt et al., 2009;

335Barrios-Quieroz et al., 2012), though the differences are often subtle and are more related to size

336rather than features of the feeding apparatus, so the lack of significant correlation here is

337unsurprising. Collection protocol (i.e., pig vs. cow bones, restrained vs. unrestrained during

338feeding) certainly provided complicating variables that could have affected bite mark expression,

339but these too failed to adequately explain the observed bite mark patterns. This leaves us with

340phylogenetic analyses of evolutionary relationships as a potential tool for synthesizing bite mark

341data and generating predictions regarding trace expression in the paleontological record. Here we

342present fossil case studies in order to test phylogenetic predictions reported in the Results

343section.

344 Crocodylus anthropophagus

345 The initial study of crocodylian bite marks by Njau and Blumenschine was specifically

346performed in order to address unusual patterns of traces present on fossils collected from the

347famous hominin site, Olduvai Gorge (2006). The possibility that crocodylians had been active

348taphonomic agents in the Olduvai environment, even predating on hominins, had been discussed

349previously (Davidson and Solomon 1990), but large-scale actualistic studies had not been

350performed to verify this interpretation. The survey of Crocodylus niloticus feeding traces by

351Njau and Blumenschine (2006), including the new bisected marks and hook scores, was fully

352consistent with the fossil marks present at Olduvai.

353 Recent analysis of Olduvai crocodylian material led to its classification as a new species

354of large, horned crocodylian, Crocodylus anthropophagus (Brochu et al. 2010). Crocodylian bite

355marks identified from the site were consistent with the size and inferred ecology of the new

356species, and with no other taxa seemingly present, a correlation between marks and specific Drumheller and Brochu | 17

357taxon was made.

358 As seen in Figure 5, C. anthropophagus is unambiguously (and accurately) predicted to

359have been capable of producing bisected marks.

360 Deinosuchus riograndensis

361 Schwimmer (2002, 2010) attributed bite marks on dinosaurian bones to Deinosuchus

362riograndensis based largely on the ovoid cross-sectional shape and the large size of the traces.

363No mention of bisected marks or other traces of a prominent carina was made. Even after the

364publication of potentially diagnostic crocodylian bite marks, including bisections (Njau and

365Blumenschine 2006), the record of Deinosuchus feeding traces has not been entirely clear

366(Brochu 2003). Large bisected marks were identified on hadrosaurid bones from the Upper

367Cretaceous of Coahuila, Mexico, which led researchers to point to D. riograndenesis as the

368potential trace maker (Rivera-Sylva et al. 2009). However, similar puncture marks on a turtle

369shell were also ascribed to this species, with no mention of bisected structures (Lehman and

370Wick 2010). Observation of both the published images and the specimen itself reveals a genuine

371absence of bisected marks on this specimen.

372 Even in the large surveys of modern taxa, bisected marks are not found on every single

373bone. In C. niloticus, the rate of bisections is ~10% of all marks occurring on 82.5% of all

374marked bones (Njau and Blumenschine 2006). Similar rates have been identified in Alligator

375mississippiensis (Drumheller and Brochu 2014). The spottiness of obvious bisections in the

376Deinosuchus bite mark literature therefore likely represents the relative paucity of current

377studies. Alternatively, Deinosuchus may have generated a smaller percentage of bisected marks,

378which, if the case, could help differentiate the species from other taxa based on a feature other

379than mark size. The potential for different rates of bisections to occur in modern crocodylian bite Drumheller and Brochu | 18

380marks has been tentatively explored using samples taken from Crocodylus porosus (Westaway et

381al. 2011) and Crocodylus niloticus (Baquedano et al. 2012). The only way to determine which (if

382either) of these proposed explanations is supported is with the identification of more marks

383associated with D. riograndensis.

384 Phylogenetic predictions made here only address presence or absence of bisected marks,

385not frequency of occurrence. Since one study does identify bisected marks associated with this

386taxon (Rivera-Sylva et al. 2009), bisections are determined to be ‘present’ in the clade, and were

387accurately predicted via the phylogenetic analysis (Fig. 5).

388 Crocodyliformes

389 This study is limited to making predictions regarding presence or absence of subscores

390within the crown group. The patterns presented above are not trans-phylogenetic (sensu

391Rothschild 2015), and should only be applied to those groups bracketed by the sampled taxa.

392However, the inclusion of non-crocodylian crocodyliforms associated with bisected marks

393provides a method for expanding these predictions beyond the bounds of the crown group. For

394example, feeding traces, including bisected marks, have been reported on unionoid bivalves

395collected from the Lower Cretaceous Cameros Basin of Spain (Bermúdez-Rochas et al. 2013).

396Characteristics of the marks were compared to known crocodylomorphs from units of

397comparable age in the Iberian Peninsula, and an association with Goniopholis was made based

398on tooth size, spacing, and shape.

399 In another case study, a fossil rich locality in Texas representing a Cretaceous delta

400system has yielded a several species of crocodyliform and a number of bite marked turtle shells

401and dinosaurian bones (Adams et al. 2015). The marks exhibit bisections similar to those

402identified in modern crocodylians (Noto et al. 2012). The largest of these marks match the size, Drumheller and Brochu | 19

403shape, and arrangement of teeth in the jaw of a new species of crocodyliform discovered at the

404site.

405 Bisected pits also have been identified on turtle and crocodyliform remains from the Late

406Cretaceous Iharkút locality in western Hungary (Botfalvai et al., 2014). Several potential actors

407were discussed in that study, including a mosasaur and several species of crocodyliform. Dental

408morphology and body size were used to exclude all of those species but one, a currently

409undescribed, “Allodaposuchus-like” specimen present at the locality, whose size and dentition

410match the morphology of the feeding traces (Botfalvai et al., 2014; 2015).

411 If future uses of phylogenetic bracketing techniques can utilize these crocodyliforms as

412datapoints, phylogenetic predictions will be able to be projected beyond just the crown group. As

413it is, these examples of bisected marks found associated with multiple different crocodyliforms

414tentatively suggest that the condition might be plesiomorphic and therefore present across a

415broad spectrum of crocodylians and their more distant relatives.

416 Ziphodont Crocodyliforms

417 Of taxa included in this analysis, only three exhibit truly ziphodont teeth: the crocodylid

418Quinkana spp. and planocraniids Boverisuchus vorax and Boverisuchus geiseltalensis. The

419planocraniids Planocrania hengdongensis and Planocrania datagensis both have laterally

420compressed, recurved teeth, but without serrations. No modern crocodylian taxa exhibit

421ziphodonty, but other modern taxa have a convergent morphological condition that can be used

422to explore how this type of dentition is reflected in the bite mark record (D’Amore and

423Blumenschine 2009).

424 Based on work with Varanus komodoensis, ziphodont teeth leave striations that are

425associated with their serrations. These marks have been shown to correlate with metrics of body Drumheller and Brochu | 20

426size in different groups (D’Amore and Blumenschine 2012). Similar marks have been identified

427in the fossil record, and striation spacing, when compared to denticle morphology, has led to

428species-level associations between bite marks and actors in both theropod dinosaurs (D’Amore

429and Blumenschine 2009) and crocodyliforms (Alexander and Burger 2001). In the latter case,

430marked perissodactyl bones were identified within the gut contents of a Middle Eocene specimen

431of Boverisuchus vorax (previously classified as Pristichampsus vorax, see Brochu 2013).

432Striations on these bones were also consistent in size and spacing to denticles found in B. vorax

433teeth.

434 Ziphodonty is present in more basal crocodyliform groups as well, and associated bite

435marks exhibit similar patterns of morphology. Striated marks found on Baurusuchus

436salgadoensis and Baurusuchus pachecoi, two sebecosuchians from the Cretaceous of Brazil,

437have been cited as evidence of intraspecific fighting within Baurusuchidae (Avilla et al. 2004;

438deVasconcellos and Carvalho 2010), and gut contents from another baurusuchid, Aplestosuchus

439sordidus, demonstrate an unambiguous trophic interaction between this species and a

440sphagesaurid crocodyliform (Godoy et al., 2014). Beyond the baudusuchids, striation size and

441spacing have also been used to associate bite marks found on plesiosaur bones from the Jurassic

442of England with the marine crocodyliform Metriorhynchus (Forrest 2003).

443 Modern crocodylian bite marks are an inappropriate proxy for marks made by ziphodont

444crocodyliforms. Therefore, reported phylogenetic predictions based solely on modern taxa are

445equally inapplicable. However, since the connection between ziphodont teeth and striated bite

446marks has been established using both actualistic and paleontologic data (D’Amore and

447Blumenschine 2009; 2012), characters expressing these conditions may be tapped instead.

448Phylogenetic predictions of presence or absence of striated bite marks, based on characters Drumheller and Brochu | 21

449related to ziphodonty, are therefore reported in Figure 7.

450 Durophagous Crocodyliforms

451 Modern crocodylians that are dietary generalists sometimes exhibit feeding choices and

452behaviors associated with durophagy. Reports of crocodyliforms regularly feeding on turtles,

453crabs, and mollusks are quite common in both extant (e.g., Valentine et al. 1972; Thorbjarnarson

4541993; Grigg and Kirshner 2015) and extinct taxa (Carpenter and Lindsey 1980; Erickson 1984;

455Fuentes 2003; Karl and Tichy 2004; Mead et al. 2006; Steadman et al. 2007; Noto et al. 2012;

456Bermúdez-Rochas et al. 2013). However, no modern species retain the dental adaptations

457associated with requisite durophagy. Additionally, the only study dealing with actualistic traces

458of durophagous behavior in modern Paleosuchus palpebrosus focused on patterns of turtle shell

459breakage rather than individual bite marks (Milàn et al. 2010), patterns which have been echoed

460in the fossil record (Fuentes 2003; Noto et al. 2012), but are not easily included in the current

461phylogenetic framework.

462 Of the taxa included in the phylogenetic analysis, some hylaeochampsids and basal

463members of Globidonta exhibit the expanded, anvil-like posterior teeth of truly durophagous

464crocodyliforms. With no extant crocodylians that exhibit this morphology to sample, and no

465actualistic research on more distantly related, durophagous taxa, it is difficult to predict how this

466feeding ecology might be expressed in the fossil record. However, from a strictly structural and

467functional point of view, it seems highly likely that bite marks generated would differ from the

468patterns made by less specialized groups. As such, these taxa are also considered to be potential

469exceptions to the phylogenetic predictions made in this analysis (Fig. 7).

470 Other Studies

471 Not all fossil bite marks can be directly associated with a particular species. When Drumheller and Brochu | 22

472crocodyliform diversity in a site is high (e.g., Irmis et al. 2011; Gianechini and de Valais 2015),

473the identification of potentially diagnostic marks and even embedded teeth cannot always

474definitively pinpoint a specific actor (e.g., Boyd et al. 2013). When species-level associations can

475be made, many methods of bite mark identification cannot be scored easily for analysis in a

476phylogenetic context. Mark size and spacing are both potentially useful features for identifying

477potential actors. Mark location on prey bone and geographic association of presumed predator

478and prey are more problematic methods of identifying trace makers, but are nevertheless often

479used. However, detailed physical descriptions of the marks themselves are required to identify

480the diagnostic traits that can be treated as codable characters. There is an extensive body of work

481describing crocodyliform bite marks on a variety of prey animals or conspecific competitors, but

482many of these published associations do not lend themselves well to phylogenetic scoring.

483Published studies specifically excluded from the analyses presented herein have been collected in

484Table 3, along with brief descriptions of the documented interactions and the method of

485identification and association. These studies were excluded based on a lack of species-level

486identification of the trace maker and/or detailed descriptions of mark morphology (i.e.,

487identifications of the associated crocodyliforms were based on the previously mentioned

488alternate criteria).

489 Multiple Subscores

490 This study predicts taxa that should or should not produce bite marks with multiple

491subscores within a phylogenetic context (Fig. 6). At the present time, there are no published

492fossil studies with which to test these predictions. Multiple subscores, in the form of trisections

493and quadrisections, were only visible under high magnification with the use of a VP-SEM. In the

494existing literature, bite marks are rarely subjected to this level of scrutiny. Future studies Drumheller and Brochu | 23

495attempting to differentiate bite marks at fine taxonomic scales should consider higher

496magnification investigation as a potential source of useful data.

497 In the meantime, large-scale patterns associated with multiple subscores in crocodylian

498bite marks remain uncertain; marks may reflect a complexity to crocodylian tooth structure and

499carina shape which has not been described previously. Alternatively, they may represent

500pathological anomalies that do not carry a phylogenetic signal. Other archosaurs are known to

501have teeth with pathological split carinae (Erickson 1995), and undescribed crocodylid material

502from the Pliocene of Ethiopia has similar pathologies (J. Thompson, pers. obs.). This aspect of

503crocodylian bite mark morphology requires further study.

504 However, if these multiple subscores represent pathological alterations to the carina of

505crocodylians, it does imply that non-pathological, freshly erupted teeth should be able to

506generate standard bisected marks. If this is assumed to be the case, and if the character state

507codings for Osteolaemus tetraspis (the only species observed to make multiple subscores, but not

508bisections), the only area of ambiguity in the tree exploring the distribution of bisections resolves

509to the bisected character state, making our predictions of this feature an unambiguously clade-

510wide phenomenon (Fig. 5).

511 CONCLUSIONS

512 Observing the anatomy, behavior, and ensuing bite marks created by a single taxon and

513then projecting those observations onto a large and historically diverse clade can be problematic.

514Among related, extant animals with similar tooth morphologies, it has been shown that

515differences in dietary niche and feeding strategy can be reflected in bite mark morphology

516(Klippel and Synstelien 2007). Ideally, samples should be taken from multiple different taxa in

517order to help determine what patterns are, and are not, actually shared across groups. However, Drumheller and Brochu | 24

518the best way to synthesize multiple sources of such data, beyond qualitatively comparing and

519contrasting patterns, has not been the subject of significant study.

520 In this instance, patterns of subscore presence or absence in crocodylians did not

521statistically correlate with any recorded variable related to collection protocol, animal size, age,

522sex, or origin. Placing the feeding traces into a phylogenetic context did indicate that bisected

523marks should be present across almost all of crown Crocodylia, and did successfully predict the

524presence of these marks in a sampling of published fossil case studies (Njau and Blumenschine

5252006; Brochu et al. 2010; Rivera-Sylva et al. 2009). Bisected marks are also predicted to occur

526among more basal groups as well, due to fossil discoveries linking bisected marks to several

527different crocodyliforms (Noto et al. 2012; Bermúdez-Rochas et al. 2013; Botfalvai et al. 2014;

5282015). Patterns pertaining to multiple subscores were less definitive, and the need for further

529research remains.

530 Exploring patterns of bite marks using the extant phylogenetic bracket (Witmer 1995)

531does have limitations – diagnostic bite mark types are not always present on every modified bone

532in an assemblage, and as actualistic data can only be collected from extant forms, it cannot

533sample now-extinct behaviors and morphologies. However, even in the absence of modern data

534collected in a phylogenetic framework, phylogenies can still direct when and where more

535distantly related proxies would be most appropriate to apply. Among crocodyliforms, this is best

536exemplified by now-extinct clades that exhibited dental adaptations related to ziphodonty and

537durophagy.

538 Comparisons between actualistic taphonomic datasets are often qualitative rather than

539quantitative, due to the highly variable nature of sample collection protocols. This has limited

540our ability to tease out large-scale patterns using statistical tests and phylogenetic techniques. Drumheller and Brochu | 25

541Instituting a truly universal method for collecting, for example, bite mark datasets may not be

542viable, considering the variety of research taxa and questions these studies might address.

543However, the use of more detailed reporting methods does open certain avenues of analysis that

544have been previously underutilized, including parsimony- (Witmer 1995) and model-based

545techniques (Pagel 1999; Pagel et al. 2004). In this case study, surveying the bite marks across

546most of the extant species within Crocodylia, indicates that statistical tests and applications of

547extant phylogenetic bracketing has great potential for making taphonomic predictions.

548 ACKNOWLEDGEMENTS

549 The Saint Augustine Alligator Farm, director J. Brueggen, and curator of reptiles D.

550Kledzik provided access to and aid working with animals. Southeastern Provisional and

551Swaggerty’s Farms provided the cow and pig samples. J. Horton, F. and J. Drumheller, and H.

552Berg helped with specimen collection and processing. Support was provided though NSF DEB

5530444133 and DEB 1257786-125748 to C. Brochu and the University of Iowa Department of

554Earth and Environmental Sciences Littlefield Family Fund to S. Drumheller. The Iowa

555Department of the State Archaeologist and the Frank H. McClung Museum of Natural History of

556Culture provided storage space and equipment for sample processing and imaging. The

557University of Iowa Central Microscopy Research Laboratories provided training and access to

558scanning electron microscopes. This study represents part of a dissertation completed in partial

559fulfillment of a PhD at the University of Iowa. Committee members included: N. Budd, J. Enloe,

560J. Adrain, H. Sims, and W. Klippel. The following people also provided helpful discussion,

561feedback, and encouragement: M. Stocker, E. Wilberg, M. Spencer, two anonymous reviewers,

562and the UI Paleontological Discussion Group.

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876

877 FIGURE CAPTIONS

878FIG. 1 .—Examples of bite mark collection protocols. A) Unrestrained Caiman latirostris. B)

879restrained Alligator sinensis. Drumheller and Brochu | 40

880

881FIG. 2 —A) Line drawing of generalized bite mark types using Binford’s (1981) classification

882scheme. B) Two pits made by SAAF A03048 Crocodylus acutus. C) Punctures made by SAAF

883A03048 Crocodylus acutus. D) Score made by SAAF 86052 Alligator sinensis. E) Furrow made

884by SAAF A05004 Crocodylus novaeguineae. Scale bars = 1 cm. Drumheller and Brochu | 41

885

886FIG. 3 —Line drawing of pitted bone comparing bisected and unbisected marks with examples of Drumheller and Brochu | 42

887associated tooth morphologies. VP-SEM images of bisected and quadrisected marks with

888margins indicated with black arrows and subscores indicated with white arrows. A) Relatively

889unworn, highly carinated Crocodylus acutus tooth associated with bisected marks. B) Worn,

890chipped C. acutus tooth associated with unbisected marks (Fig. 2) and sometimes microstriations

891(Fig. 4A). C) Bisected score made by SAAF A04004 Crocodylus johnsoni. D) Bisected pit made

892by SAAF A05006 Crocodylus novaeguineae. E) Quadrisected score made by SAAF 88130

893Alligator sinensis. F) Quadrisected score made by SAAF A04004 C. johnsoni. A and B courtesy

894E. Wilberg. Scale bars = 5 mm. Drumheller and Brochu | 43

895

896FIG. 4 —Secondary alterations made by modern crocodylian trace makers. A) SAAF A01025 A.

897mississippiensis puncture with depressed fractures and fracture lines indicated with a black

898arrow. Microstriations within drag out scores indicated with a white arrow. B) SAAF ‘Fluffy’ A.

899mississippiensis puncture, indicated with a black arrow, and a depressed fracture, indicated with

900a white arrow. C) SAAF A01025 A. mississippiensis spiral fracture. D) SAAF A05004 C. Drumheller and Brochu | 44

901novaeguineae possible mark from a broken tooth with irregular scoring with microstriations

902indicated with a black arrow. Photograph scale bars (A, B, and C) = 1 cm. VP-SEM scale bar (D)

903= 1 mm.

904

905FIG. 5 —Phylogenetic tree showing character states for bisected bite mark characters across key

906clades within Eusuchia. Drumheller and Brochu | 45

907

908FIG. 6 —Phylogenetic tree showing character states for multiple subscore characters across key

909clades within Eusuchia. Drumheller and Brochu | 46

910

911FIG. 7 —Phylogenetic tree showing character states for dental characters across key clades

912within Eusuchia that are related to ziphodonty and durophagy. Drumheller and Brochu | 47

913

914 TABLES

915TABLE 1 —Types of bite marks and modifications caused by crocodylians, organized by species.

916X = Present in this survey. 1 = Present in Njau and Blumenschine, 2006. 2 = Present in Drumheller and Brochu | 48

917Westaway et al., 2011, Wood 2008, and Chattopadhyay et al. 2013. 3 = Present in Cupal-Magaña

918et al. 2010. 4 = Present in Caldicott et al., 2005 and Westaway et al., 2011. s s s s s s s s s t e e e e n n n i w i r r r o o o P c o o u u r ti ti ti e t t c r c c c c c p S u e e e a S n F s s s r i i i u F r r P B T d a u Q

Alligator X X X X X X mississippiens is

Alligator X X X X X sinensis

Caiman X X X crocodilus

Caiman X X latirostris

Caiman X X X X yacare

Crocodylus X X X X 3 acutus

Crocodylus X X intermedius

Crocodylus X X X X johnstoni

Crocodylus X X X mindorensis

Crocodylus X X X moreletii

Crocodylus X 1 X X 4 niloticus

Crocodylus X X X X X novaeguineae Drumheller and Brochu | 49

Crocodylus X X X 2 2 porosus

Crocodylus X X X rhombifer

Crocodylus X X siamensis

Mecistops X X cataphractus

Melanosuchu X X X s niger

Osteolaemus X X X tetraspis

Paleosuchus X palpebrosus

Paleosuchus X X trigonatus

Tomistoma X X X X X schlegelii

919

920TABLE 2 —Detailed results of the statistical analyses performed to test the independence of

921subscore expression from the listed variables. Abbreviations: SS = sum of squares, d.f. = degrees

922of freedom.

923

Chi-squared Tests n d.f. Chi-square p-value

Bone type (pig vs. cow) 60 33 24.99 0.840

Sex (male vs. female) 50 31 19.992 0.936

Origin (captive vs. wild) 46 20 14.954 0.779

Protocol (restrainted vs. not) 59 42 28.267 0.948

Snout ecomorph (Brochu, 2001) 61 36 41.487 0.244 Drumheller and Brochu | 50

924

ANOVA Tests n SS (between groups) SS (within groups) F p-value

Age in years 42 17.1905 5190.71 0.1325 0.718

Total length in cm 54 138.924 377390 0.01914 0.891

Head length in cm 54 0.653432 6753.01 0.005032 0.944

Snout-vent length in cm 54 38.5195 94477.9 0.0212 0.885

Mass in kg 49 233.915 155328 0.07078 0.791

925

Kruskal-Wallis Tests Shapiro-Wilk W Shapiro-Wilk p-value Kruskal-Wallis p-value

Age in years 0.9088 0.003 0.431

Total length in cm 0.9024 0.0003 0.893

Head length in cm 0.9223 0.002 0.979

Snout-vent length in cm 0.9425 0.012 0.830

Mass in kg 0.7358 4.83E-08 0.992

926

927TABLE 3 —Literature addressing fossil bite marks associated with crocodyliforms that were not

928included in the phylogenetic analysis. Data presented includes (from left to right): paper citation,

929acting taxon, marked taxon, geologic age, method of associating marks with actors.

Citation Acting taxa Marked Taxa Age Notes Boyd et al., 2013 Crocodyliformes Hypsilophodontid Cretaceou Bisected pit, s embedded tooth Noto et al., 2012 Crocodyliformes, Turtle, Hadrosaur Cretaceou Bisected marks, n. sp. s serial marks Casal et al., 2013 Crocodyliformes Aniksosaurus Cretaceou Bisected marks, Drumheller and Brochu | 51

darwini s hook scores, serial marks, interdental spacing Gianechini and de Crocodyliformes? Buitreraptor Cretaceou Mark shape, Valais, 2015 gonzalezorum s distribution Botfalvai et al., 2014, “Allodaposuchus- bothremydid Cretaceou Bisected marks, 2015 like” turtle, s size, interdental Crocodyliformes Iharkutosuchus spacing Martin, 2013 Dyrosauridae or Dyrosauridae Paleocene Mark size, shape, Eusuchian association Milàn et al., 2011 Crocodylia Chelonionid turtle Paleocene Round mark shape Evgen et al., 2012 Crocodylia indet. Cheloniidae indet. Eocene Comparison to Noto et al., 2012 Davidson and Solomon, Crocodylus Homo habilis Plio- Comparison to 1990 Pleistocen modern actors, e excluded other possible actors Fuentes, 2003 Asiatosuchus Neochelys Eocene Comparison to dentition of possible actors, association Mead et al., 2006 Crocodylus Horse, Turtle Plio- Round mark shape, Pleistocen association e Mikulás et al., 2006 Crocodylus? Many different Miocene Comparison to vertebrates tooth shape Steadman et al., 2007; Crocodylus Turtle Holocene Round mark shape, Morgan and Albury, rhombifer association 2013 Cisneros, 2012 Crocodylus acutus Proboscidean Pleistocen Round mark shape, e interdental spacing Buffetaut, 1983 Tilemsisuchus Tilemsisuchus Eocene Interdental spacing, lavocati lavocati mark locations Erickson, 1984 Leidysuchus Turtle Paleocene Mark size, formidabilis interdental spacing, association Williamson, 1996 ?Brachychampsa ?Brachychampsa Cretaceou Bite mark shape sealetyi sealetyi s and location Karl and Tichy, 2004 Phosphatosaurus Palaeomedusa? Eocene Comparison to gavialoides dentition, association Katsura, 2004 Toyotamaphimeia Toyotamaphimeia Pleistocen Bite mark shape machikanensis machikanensis e and location Hastings et al., 2015 Anthracosuchus Turtle Paleocene Mark size, balrogus association Mackness et al., 2010 Pallimnarchus Pallimnarchus Pliocene Mark size, pollens pollens association 930

931 Drumheller and Brochu | 52

932 SUPPLEMENTARY MATERIAL

933SUPPLEMENTARY FIGURE 1 —Eusuchian phylogeny, generated from a matrix of 189 characters

934and including 124 ingroup taxa. Solid lines represent the strict consensus tree. Dotted lines

935indicate areas in which the topology differs in the Adams consensus tree. Drumheller and Brochu | 53

936 Drumheller and Brochu | 54

937SUPPLEMENTARY TABLE 1 —Vital statistics and collection protocols for sampled specimens;

938abbreviations: Y = yes; N = no; M = male; F = female; C = captive; W = wild; n/a = non-

939applicable/unrecorded. t s h # h s n

t t n e n t s g n e g d o l n i s v e o h n o e n i t i i - i e e p x e g e t g t c t g c s l i l g e i c a

u e s e o m e s a r l e s d e o a p n m o a - s w a c s s i t n i d e c s o b a t a h u h t q g n

Alligator 22Y, e 185 l mississippiensis - 970 pi 11M, 314 45 161 .97 American Alligator 62 Y g M 23D cm cm cm kg C N N unrestrained

co 143 990 w 296 41 151 .6 13 ? M ~31Y cm cm cm kg ? N N unrestrained

co 31. A05 w 244 5 120 001 ? M adult cm cm cm ? ? N N unrestrained

A01 co 402 57 193 025 Y w M >56 cm cm cm ? W Y N unrestrained

5Y, 15. 62. A00 pi 11M, 122 25 25 7.8 241 g ? 5D cm cm cm kg C N N restrained

6Y, 185 25. 95. 25. 991 pi 10M, .5 5 25 4 06 Y g ? 9D cm cm cm kg W Y N restrained

5Y, 73. 12. A00 pi 11M, 146 19 5 6 268 Y g ? 5D cm cm cm kg C N N restrained

971 304 41 158 unrestrained 03 M adult cm cm cm ? ? N N with 97064

22Y, 45. 970 co 11M, 353 5 169 unrestrained 64 Y w M 24D cm cm cm ? C N N with 97103

Fluf co fy Y w M adult ? ? ? ? ? N N unrestrained

Wal co ly Y w ? adult ? ? ? ? ? N N unrestrained

Mot Y co F adult ? ? ? ? ? Y N unrestrained Drumheller and Brochu | 55

her w

402 643 co 18 Y w ? adult ? ? ? ? ? N N unrestrained

tt 20. 105 14. 008 pi juveni 160 5 .5 8 52 g ? le cm cm cm kg ? Y N restrained

19Y, 18. 14. Alligator sinensis - 860 pi 9M, 155 8 81 6 Chinese Alligator 52 Y g M 15D cm cm cm kg C N N restrained

19Y, 17. 11. 860 pi 9M, 141 5 74 8 53 Y g F 15D cm cm cm kg C Y N restrained

10Y, 136 16. 74. 13. 950 pi 9M, .9 1 3 5 74 Y g F 1D cm cm cm kg C Y N restrained

13Y, 881 pi 9M, 106 14 55 3.5 30 Y g F 14D cm cm cm kg C N Y restrained

21. Caiman crocodilus - 960 pi 164 5 98 25 Spectacled Caiman 54 Y g M adult cm cm cm kg ? Y N restrained

no pi tag Y g ? ? ? ? ? ? ? Y N restrained

104 321 pi 089 Y g ? ? ? ? ? ? ? N N restrained

Caiman latirostris - 20Y, Broad-snouted 860 pi 5M, 179 21 99 27 N Caiman 12 Y g F 7D cm cm cm kg C ? N restrained

9Y, 21. 26. 891 pi 11M, 159 5 87 2 25 Y g F 10D cm cm cm kg C N N restrained

16Y, 152 88. 22. Caiman yacare - 960 pi 10M, .5 20 5 7 Yacare Caiman 28 Y g F 2D cm cm cm kg C N N restrained

18Y, 21. 890 pi 6M, 148 3 91 19 38 Y g F 21D cm cm cm kg C Y Y restrained Drumheller and Brochu | 56

18Y, 60. 890 pi 6M, 5 7.5 30 39 Y g F 21D cm cm cm ? C N N restrained

10Y, 18. 63. Crocodylus acutus - 960 co 3M, 117 5 5 5.6 American Crocodile 49 Y w ? 9D cm cm cm kg C Y N restrained

33Y, 40. 150 90. A03 co 6M, 287 5 .5 8 048 Y w F 23D cm cm cm kg C N N unrestrained

Crocodylus 18Y, 312 173 intermedius - 912 co 11M, .5 44 173 .25 Orinoco Crocodile 77 Y w M 22D cm cm cm kg C N N unrestrained

Crocodilus johnsonii 27Y, 19. - Johnston's A04 pi 7M, 118 5 66 5.2 Crocodile 003 g? F 0D cm cm cm kg C N N restrained

36. 970 pi 217 35 118 3 16 Y g M adult cm cm cm kg ? N N restrained

27Y, 87. 11. 930 pi 7M, 157 27 5 8 42 Y g F 7D cm cm cm kg C N N restrained

27Y, A04 pi 7M, 132 23 75 7.8 004 Y g F 7D cm cm cm kg C Y Y restrained

Crocodilus 4Y, 11. 45. mindorensis - A03 pi 10M, 85 5 5 2.2 Philippine Crocodile 034 g ? 9D cm cm cm kg C restrained

4Y, 36. A03 pi 10M, 69 9.5 5 1.2 036 Y g ? 9D cm cm cm kg C Y N restrained

4Y, A03 pi 10M, 70 9.5 39 1.4 033 Y g F 9D cm cm cm kg C N N restrained

43Y, 37. 108 Crocodylus moreletii 990 co 6M, 284 5 154 .9 - Morelet's Crocodile 09 Y w M 20D cm cm cm kg W N N unrestrained

8Y, Crocodylus niloticus A01 pi 0M, 122 15 62 7 - Nile Crocodile 027 Y g ? 13D cm cm cm kg C N N restrained Drumheller and Brochu | 57

239 135 86. 932 co .5 36 .5 5 20 Y w M adult cm cm cm kg ? Y N unrestrained

25Y, 37. 93. 990 co 1M, 261 5 134 3 14 Y w M 4D cm cm cm kg ? N N unrestrained

Crocodylus 6Y, 116 17. novaeguineae - New A05 pi 0M, .5 5 64 6.7 Guinea Crocodile 013 g? M 28D cm cm cm kg C restrained

6Y, A05 pi 0M, 97 15 53 3.4 009 g? F 28D cm cm cm kg C restrained

6Y, A05 pi 0M, 104 16 56 3.8 006 Y g F 28D cm cm cm kg C Y N restrained

6Y, 12. A05 pi 0M, 82 5 40 3.8 012 g? M 28D cm cm cm kg C restrained

290 33. 149 unrestrained, A05 co .5 75 .5 123 tooth broken 004 Y w M adult cm cm cm kg W N Y (top, left, front)

Crocodylus palustris n/ n/ n/ n/ n/ n/ - Mugger n/a a a a n/a n/a n/a n/a n/a a a a edentulous

Crocodylus porosus - Salt Water San co Crocodile dy w F ? ? ? ? ? C N N unrestrained

Crocodylus 17Y, 111 rhombifer - Cuban 890 co 4M, 209 27 .5 63 Crocodile 33 Y w F 17D cm cm cm kg C Y N restrained

14Y, 186 24. 98. 29. tooth broken 913 co 7M, .5 5 5 5 (bottom, right, 00 Y w F 1D cm cm cm kg C Y N middle)

Crocodilus 36. 86. siamensis - Siamese 912 pi 263 5 139 6 Crocodile 73 Y g M adult cm cm cm kg W N N unrestrained

5Y, A00 pi 10M, 124 17 62 4.2 104 g? F 26D cm cm cm kg C N N restrained

Gavialis gangeticus - n/a n/ n/ n/ n/a n/a n/a n/a n/a n/ n/ n/ stressed by Indian Gharial a a a a a a enclosure, off Drumheller and Brochu | 58

limits

Mecistops cataphractus - 11Y, Slender-snouted 960 pi 9M, 118 20 63 4.8 Crocodile 12 Y g F 3D cm cm cm kg C N N restrained

11Y, 960 pi 9M, 115 18 51 3.8 15 Y g F 1D cm cm cm kg C N N restrained

Melanoshuchus 303 46. niger - Black 912 co .5 35 5 143 Caiman 66 Y w F adult cm cm cm kg W Y N unrestrained

Osteolaemus 182 23. 34. tetraspis - African 960 pi .5 5 102 6 Dwarf Crocodile 79 Y g M adult cm cm cm kg ? N N restrained

24Y, 14. 940 pi 9M, 135 18 74 4 04 g F 9D cm cm cm kg C N N unrestrained

7Y, 17. 69. 990 pi 2M, 124 8 3 9.4 04 Y g F 20D cm cm cm kg C N N restrained

Paleosuchus 15Y, 125 12. palpebrosus - Dwarf 930 pi 11M, .5 17 71 2 Caiman 72 g? M 24D cm cm cm kg C N N restrained

15Y, 18. 14. 930 pi 11M, 136 5 77 6 71 Y g M 24D cm cm cm kg C N N restrained

15Y, 15. 930 pi 11M, 123 5 66 9.5 73 Y g M 24D cm cm cm kg C N N restrained

Paleosuchus 20Y, 64. trigonatus - Smooth- 850 pi 9M, 170 26 99 5 fronted Caiman 29 Y g M 19D cm cm cm kg C Y N unrestrained

6Y, 15. 870 pi 5M, 139 21 82 4 28 Y g F 23D cm cm cm kg C Y N unrestrained

2Y, 19. A04 pi 1M, 154 23 89 1 tooth broken 031 Y g M 22D cm cm cm kg C N N (top, right, front)

850 Y pi M adult 160 24. 99. 28 W N N restrained 28 g cm 8 9 Drumheller and Brochu | 59

cm cm kg

Tomistoma 33Y, 40. 150 90. schlegelii - False A01 co 6M, 287 5 .5 8 Gharial 020 Y w F 17D cm cm cm kg W N N unrestrained

404 212 252 912 co .5 51 .5 .5 83 Y w M adult cm cm cm kg W Y N unrestrained

940

941