New Morphological Evidence for the Phylogeny of Artiodactyla, Cetacea, and Mesonychidae

Home , Agriochoerus, Andrewsarchus, Anthracotheriidae, Arctocyon, Cainotheriidae, Cainotherium

PUBLISHED BY THE AMERICAN MUSEUM OF NATURAL HISTORY CENTRAL PARK WEST AT 79TH STREET, NEW YORK, NY 10024 Number 3344, 53 pp., 11 ®gures August 28, 2001

JONATHAN H. GEISLER1

ABSTRACT Parsimony-based analyses of a data set including 68 taxa coded for 186 morphological characters corroborate monophyly of Artiodactyla (even-toed ungulates), Suiformes (hippos, pigs, peccaries), Neoselenodontia (camels, deer, cows), and Acreodi (whales, dolphins, porpoises, mesonychids). Additional ®ndings include a sister-group relationship between Cain- otheriidae and Cameloidea (Camelidae ϩ Oromerycidae), Elomeryx as the sister group to all other suiform artiodactyls, Protoceratidae as the basal branch of Neoselenodontia, and paraphyly of Mesonychidae. The molecule-based groups Whippomorpha (whales, dolphins, hippos), Cetruminantia (whales, deer, cows), and Artiofabula (whales, cows, pigs) are contradicted by these data and occur together in trees that are at least 25 steps longer than the most parsimonious ones. In terms of tree length, the molecule-based topology is contradicted by morphological data with and without extinct taxa, and unlike previous, morphology-based analyses, the exclusion of Cetacea from the clade of living artiodactyls is not dependent on the inclusion of extinct taxa. Artiodactyla is diagnosed in all most parsimonious trees by several characters, including a short mastoid process of the petrosal, absence of an alisphenoid canal, and presence of an entocingulum on P4. Some previously suggested artiodactyl synapomorphies, such as an enlarged facial exposure of the lacrimal and absence of contact between the frontal and alisphenoid, are shown to be synapomorphies of more exclusive clades within Artiodactyla.

INTRODUCTION the most hotly debated issues in mammalian systematics, as shown by a review of the The phylogenetic position of Cetacea controversy surrounding cetacean and artio- (whales, dolphins, and porpoises) is one of dactyl phylogeny (Luo, 2000), a volume on

1 Graduate Student, Division of Paleontology, American Museum of Natural History Currently: Postdoctoral Re- search Assistant, Division of Vertebrate Zoology (Mammalogy).

Copyright ᭧ American Museum of Natural History 2001 ISSN 0003-0082 2 AMERICAN MUSEUM NOVITATES NO. 40 cetacean origins (Thewissen, 1998), and nu- Geisler (1999). Although these studies have merous analytical studies (e.g., Gatesy et al., made detailed comparisons between morpho- 1999a, 1999b; Nikaido et al., 1999; O'Leary, logical and molecular data possible, much of 1999; O'Leary and Geisler, 1999; Shima- the data concerning the phylogeny within Ar- mura et al., 1999). Almost all morphology- tiodactyla have yet to be included. This study based studies have found Mesonychidae (or has four primary goals: (1) to add taxa and one or more mesonychids) to be the sister new characters to previously published mor- group to Cetacea, and have found Artiodac- phological data sets (Geisler and Luo, 1998; tyla (even-hoofed ungulates, including cam- O'Leary and Geisler, 1999; Luo and Ginger- els, pigs, and deer) to be monophyletic (Van ich, 1999); (2) to determine what taxonomic Valen, 1966; Thewissen, 1994; Geisler and groups these characters support, as well as Luo, 1998; O'Leary, 1998a; O'Leary and the degree of support for these groups; (3) to Geisler, 1999; Luo and Gingerich, 1999) (®g. determine if the evidence for the exclusion 1A). By contrast, the vast majority of DNA of Cetacea from the clade of extant artiodac- sequence-based studies have found strong tyls is restricted to the data for extinct taxa; evidence for two clades that render Artio- and (4) to test alternative phylogenies, par- dactyla paraphyletic: (1) Whippomorpha, ticularly those based on molecules. which includes Hippopotamidae and Ceta- cea, and (2) Cetruminantia, which includes TAXONOMY Whippomorpha and Ruminantia (includes deer, cows, antelope, chevrotain, and many The molecule-based and morphology- others) (Gatesy et al., 1996, 1999a, 1999b; based hypotheses of artiodactyl and cetacean Gatesy, 1997, 1998; Montgelard et al., 1997; phylogeny not only differ in the phylogenetic Shimamura et al., 1997, 1999; Ursing and position of extant cetaceans and extant artio- Arnason, 1998; Nikaido et al., 1999; Klei- dactyls, but they are based on signi®cantly neidam et al., 1999) (®g. 1B). The incongru- different, yet slightly overlapping, sets of ence between morphological and molecular taxa. The disparity in topology and in the data is statistically signi®cant (O'Leary, choice of taxa highlights the confusion 1999), and there are no plausible explana- caused by phylogenetic de®nitions for taxa. tions for the con¯ict between the two classes Some of the taxa discussed in this paper have of data. not been properly or explicitly de®ned, while Incongruence between different classes of the use of other taxa varies between authors. data can be objectively measured only if the For instance, Artiodactyla has either not in- character data have been compiled in the cluded Cetacea (Simpson, 1945; McKenna form of a character/taxon matrix. The spe- and Bell, 1997), has included Cetacea (Graur ci®c observations that lead to the incongru- and Higgins, 1994; Xu et al., 1996; Kleinei- ence can be isolated and reexamined if the dam et al., 1999), or has been replaced by data are in a matrix form. Although there the taxon Cetartiodactyla, which includes have been numerous studies on artiodactyl Cetacea (Montgelard et al., 1997; Nikaido et phylogeny (e.g., Matthew, 1929, 1934; Janis al., 1999). The inclusion of Cetacea within and Scott, 1987; Gentry and Hooker, 1988; Artiodactyla, as advocated by Graur and Hig- Scott and Janis, 1993) and others on cetacean gins (1994), Xu et al. (1996), and Kleinei- phylogeny (e.g., Muizon, 1991; Fordyce, dam et al. (1999), can be justi®ed if their 1994; Messenger and McGuire, 1998; Luo molecule-based cladograms are the most par- and Gingerich, 1999; Uhen, 1999), there simonious hypotheses and if they use a phy- have been few studies that have made com- logenetic de®nition for Artiodactyla. parisons between members of both taxonom- Taxa that have been de®ned using phylo- ic groups. Geisler and Luo (1998) presented genetic taxonomy (sensu stricto de Quieroz the ®rst cladistic analysis of morphological and Gauthier, 1990) are not used in this paper data that included basal cetaceans as well as because taxon membership varies signi®- several artiodactyls. Their work was signi®- cantly with the choice of cladogram. To cantly expanded and improved upon by Geis- avoid confusion, only group-based de®ni- ler and O'Leary (1997) and O'Leary and tions are used here. The content of each 2001 GEISLER: ARTIODACTYLA, CETACEA, MESONYCHIDAE 3 group follows McKenna and Bell (1997), Geisler and Luo, 1998; O'Leary and Geisler, with the following exceptions. Suiformes is 1999). McKenna and Bell (1997) did not rede®ned here as the group including An- provide a name for the group that includes thracotheriidae, Entelodontidae, Hippopo- Cetacea, Artiodactyla, Mesonychidae, Hapa- tamidae, Suidae, and Tayassuidae but exclud- lodectidae, and Andrewsarchus. Following ing Ruminantia, Camelidae, Oromerycidae, Thewissen (1994) and Geisler and Luo Cainotheriidae, Oreodontoidea, Xiphodonti- (1998), I use Paraxonia for this group, which dae, Mixtotherium, Cebochoerus, Gobiohyus, McKenna and Bell listed as a junior syno- Homacodon, and all species of Diacodexis. nym of Artiodactyla. Simpson (1945) and McKenna and Bell (1997) placed all nonselenodont artiodactyls PREVIOUS STUDIES in Suiformes, which makes the group paraphyletic with respect to virtually all mor- Molecular and morphological studies on phology-based hypotheses of artiodactyl the phylogenetic position of Cetacea have phylogeny (Matthew, 1934; Gentry and been reviewed by Gatesy (1998) and Hooker, 1988; Geisler and Luo, 1998; O'Leary and Geisler (1999); only recently O'Leary and Geisler, 1999). The present re- published papers not reviewed by these au- de®nition maintains traditional members of thors will be described here. Gatesy (1998) this group, such as Suidae and Hippopotam- presented new nucleotide sequences for sev- idae, but excludes former members so that it eral mammalian taxa and performed com- becomes monophyletic, at least based on bined and partitioned analyses of his data set, morphological data. If future parsimony- which included over 4500 aligned nucleotide based phylogenies have a paraphyletic Sui- positions. His analysis with all genes com- formes, I suggest that this group be aban- bined and most of his partitioned analyses doned instead of being rede®ned. supported a sister-group relationship between As in Simpson (1945), but unlike McKen- Hippopotamidae and Cetacea, as well as a na and Bell (1997), Suina is used to denote larger clade including these two taxa plus the group including Suidae and Tayassuidae Ruminantia. These controversial clades that to the exclusion of Hippopotamidae and oth- result in artiodactyl paraphyly received sig- er suiform artiodactyls. McKenna and Bell ni®cant branch support and had bootstrap (1997) did not recognize this clade in their values over 90% (Gatesy, 1998). Luckett and classi®cation and instead listed Suina as a ju- Hong (1998) presented an exhaustive analy- nior synonym of Suinae. Following Viret sis of selected morphological characters and (1961) and Webb and Taylor (1980), but con- previously published or available cyto- trary to McKenna and Bell (1997) and Gen- chrome b sequences. They found that two try and Hooker (1988), Ruminantia, as used characters, the double-trochleated astragalus here, does not include the Amphimerycidae. and a trilobed, deciduous, fourth lower pre- Instead, Amphimerycidae and Xiphodonti- molar, are rare among mammals but occur in dae are considered as the only two families every extant and extinct artiodactyl genus for in the group Xiphodontoidea, named by Viret which these anatomical regions are pre- (1961). Use of the group Neoselenodontia served. They also determined that most of follows Webb and Taylor (1980) and in- the nucleotides that supported the Hippopo- cludes Camelidae, Oromerycidae, Ruminan- tamidae ϩ Cetacea clade exhibit some level tia, Protoceratidae, and Xiphodontoidea but of homoplasy across all mammals. Based on excludes Oreodontoidea. McKenna and Bell these observations, Luckett and Hong (1998) (1997) elevated Acreodi to subordinal rank concluded that existing molecular data are and placed triisodontids, mesonychids, and not suf®cient to overturn artiodactyl mono- hapalodectids inside it; however, I follow the phyly; however, other genes that corroborate use of Acreodi by Prothero et al. (1988) to Whippomorpha and Cetruminantia (e.g., ␬ denote the group including Hapalodectidae, and ␤ casein and ␥ ®brinogen) were not dis- Mesonychidae, and Cetacea. Andrewsarchus cussed in much detail. is excluded from Acreodi based on previous Ursing and Arnason (1998) sequenced the morphological studies (O'Leary, 1998a; entire mitochondrial genome of Hippopota- 4 AMERICAN MUSEUM NOVITATES NO. 40 mus amphibius and included it in a phylo- monophyletic Whippomorpha, Cetruminan- genetic analysis with 15 other mammals. tia, and Artiofabula (®g. 1B). Maximum likelihood, maximum parsimony, O'Leary (1999) presented the ®rst com- and neighbor-joining methods produced op- bined morphological and molecular analysis timal trees that supported a hippopotamid that included signi®cant numbers of ceta- and cetacean clade as well as a hippopotam- ceans and artiodactyls. The morphological id, cetacean, and ruminant clade. Milinkov- data were based on the matrix of O'Leary itch et al. (1998) retrieved nucleotide se- and Geisler (1999), and the molecular data quences of the ␣-lactalbumin protein from came primarily from Gatesy et al. (1996) and several artiodactyls and cetaceans. Using a Gatesy (1997). O'Leary (1999) found the in- variety of phylogenetic methods, they found congruence between the neontological (al- additional support for artiodactyl paraphyly; most entirely molecular) and osteological however, their taxonomic sampling was poor partitions to be statistically signi®cant ac- (only four cetaceans and four artiodactyls). cording to the partition-homogeneity test of Montgelard et al. (1998) completed the ®rst Farris et al. (1995). Sequence alignments and phylogenetic analysis of higher level artio- analyses of the combined matrix were per- dactyl phylogeny that combined morpholog- formed using nine different combinations of ical and molecular data; however, little new parameters (e.g., gap cost, transition/trans- data were presented, Cetacea was not includ- version ratio), and all resulted in a paraphy- ed, and the ingroup only included six taxa. letic Artiodactyla. Apparently all most par- They found substantial support for Suina simonious trees from all analyses had the (Suidae ϩ Tayassuidae) but weak support for Hippopotamidae and Cetacea clade to the ex- a suiform clade of Suina ϩ Hippopotamidae. clusion of other extant artiodactyls (O'Leary, Gatesy et al. (1999b) added several pre- 1999). viously published data sets to that of Gatesy Shimamura et al. (1999) expanded upon (1998), resulting in a 64% increase in the the work of Shimamura et al. (1997) by se- quencing and comparing more nucleotide se- number of informative characters. They also quences for several different SINEs (short inde®ned and implemented several new meth- terspersed repetitive elements) found in some ods of evaluating nodal support, resulting in artiodactyls and cetaceans. The identi®cation the discovery of signi®cant amounts of hid- of related SINEs in Sus (pigs) and Tayassu den support for the Hippopotamidae Ce- ϩ (peccaries) but not in Camelus (camels) cor- tacea clade as well as the more inclusive roborated the phylogeny of Gatesy (1998: clade including Cetacea, Hippopotamidae, ®g. 16), where Suidae and Tayassuidae are and Ruminantia (Gatesy et al., 1999b). Four more closely related to cetaceans than is Ca- new sequences were added to a growing melidae. Nikaido et al. (1999) presented new body of molecular data by Gatesy et al. SINE and LINE (long interspersed element) (1999a). These new sequences plus previ- data, including the distribution of SINEs at ously published data were compiled into a 10 new loci. In addition to corroborating the data set (WHIPPO-1), which resulted in a phylogeny of Shimamura et al. (1997, 1999), 67% increase in the number of informative they found four insertions that support the characters over Gatesy et al. (1999b). The Hippopotamidae and Cetacea clade. Nikaido most parsimonious trees for the WHIPPO-1 et al. (1999) asserted that SINEs are virtually matrix were the same as those for the matrix homoplasy-free and that their insertions can analyzed by Gatesy et al. (1999b) but had be treated as irreversible; however, consid- increased support for the controversial clades ering the small number of SINE characters that group cetaceans with extant artiodactyls. and the large amount of missing data in the The cost of artiodactyl monophyly was ap- matrix of Nikaido et al. (1999), such claims proximately 120 steps (Gatesy et al., 1999a). are premature. As with all other phylogenetic Gatesy et al. (1999a) also presented and an- data, their only source of validation is con- alyzed a larger matrix dubbed WHIPPO-2. gruence with preexisting, independent data, Like many previous molecule-based hypoth- in this case nucleotide distributions. eses, all most parsimonious trees had a Kleineidam et al. (1999) sequenced pan- 2001 GEISLER: ARTIODACTYLA, CETACEA, MESONYCHIDAE 5

Fig. 1. Previous phylogenetic hypotheses for artiodactyls, cetaceans, and mesonychids. Taxa not included in this study were pruned from each tree, and taxa shared between the previous two studies are in boldface. A. The most parsimonious tree for the morphological data analyzed by O'Leary and Geisler (1999). Note that Artiodactyla, Neoselenodontia, and Suiformes are monophyletic. B. The strict consensus of the shortest trees for the WHIPPO-2 molecular data set of Gatesy et al. (1999a). Unlike O'Leary and Geisler (1999), Artiodactyla, Neoselenodontia, and Suiformes are paraphyletic, while Whippomorpha, Cetruminantia, and Artiofabula are monophyletic. creatic ribonuclease genes for eight artiodac- O'Leary and Geisler (1999) presented a tyls and cetaceans. A phylogenetic analysis detailed phylogenetic analysis of a matrix of of these sequences plus previously published 40 taxa scored for 123 morphological char- data supported a Hippopotamus and Cetacea acters, a signi®cant increase in both charac- clade; however, unlike other recent molecular ters and taxa over the data set used by Geis- studies, Suidae (pigs) instead of Camelidae ler and Luo (1998). Their most parsimonious was the sister group to a clade including all trees included a monophyletic Artiodactyla, other extant artiodactyls and Cetacea. Wad- Mesonychidae ϩ Cetacea, Neoselenodontia, dell et al. (1999), in a summary paper for the and Suiformes (O'Leary and Geisler, 1999) 1998 ``International Symposium on the Ori- (®g. 1A). They found that the recovery of gin of Mammalian Orders'', presented no artiodactyl monophyly hinged on the addi- new data or analyses but did name several tion of extinct taxa to the phylogenetic anal- controversial clades of artiodactyls supported ysis. Thewissen and Madar (1999) described by molecular data. The clade of Cetacea ϩ the functional morphology of the ankle in Hippopotamidae was named Whippomorpha, ungulates, listed eight phylogenetically in- the Whippomorpha ϩ Ruminantia clade was formative characters of this region (some named Cetruminantia, and the Whippomor- new and others previously described), and pha ϩ Suidae (and presumably Tayassuidae) presented a character matrix of ankle char- was named Artiofabula (Waddell et al., acters scored for a diverse group of mam- 1999). mals. Most of the new data in the matrix was 6 AMERICAN MUSEUM NOVITATES NO. 40 based on several astragali that were referred ChM PV Charleston Museum vertebrate pale- to cetaceans by Thewissen et al. (1998); ontology collection, Charleston, however, O'Leary and Geisler (1999) ques- South Carolina tioned their referral because it is based on GSM Georgia Southern Museum, States- boro, Georgia. size and faunal components, not on direct as- GSP-UM Geological Survey of Pakistan/Uni- sociation with de®nitive cetacean remains. versity of Michigan, Ann Arbor The matrix of Thewissen and Madar (1999) H-GSP Howard University/ Geological Sur- was analyzed by calculating the ®t of all vey of Pakistan, Washington, D.C. characters to the tree of Prothero et al. (1988) IVPP Institute of Vertebrate Paleontology or to modi®ed versions of this tree. They and Paleoanthropology, Beijing, China state that tarsal morphologies are ``also con- MAE Mongolian Academy of Sciences± sistent with the inclusion of cetaceans in ar- American Museum of Natural History Paleontological Expeditions, collec- tiodactyls, if one assumes that the wide arc tion to be deposited at the Mongolian of rotation of the trochleated head was lost Academy of Sciences, Ulaan Bataar during the origin of Cetacea'' (Thewissen MCZ Museum of Comparative Zoology, and Madar, 1999: 28). However, the only Harvard University, Cambridge, Mas- cladogram in their ®gure 2 that had Cetacea sachusetts grouped within Artiodactyla was ®ve steps SMNS Staatliches Museum fuÈr Naturkunde, longer than alternative topologies that placed Stuttgart, Germany Cetacea outside of, but still the sister group USNM National Museum of Natural History, to, Artiodactyla. Smithsonian Institution, Washington, D.C. Luo and Gingerich (1999) described the YPM Yale Peabody Museum, New Haven, basicrania of several basal cetaceans and me- Connecticut sonychids, determined the homologs of high- YPM-PU Princeton University collection (now ly derived cetacean basicranial structures in at Yale Peabody Museum) other terrestrial mammals, and presented a parsimony-based analysis of 64 basicranial MATERIALS AND METHODS characters. Their phylogenetic analysis supported a sister group relationship between TAXON SAMPLING Cetacea and Mesonychidae, and they listed In general, taxa were chosen to adequately several characters that support this clade; sample the diversity of Artiodactyla, Meson- however, artiodactyl monophyly was not ychidae, and Cetacea (O'Leary and Geisler, tested because only one artiodactyl taxon, 1999; method 3 of Hillis, 1998). Most OTUs Diacodexis, was included. O'Leary and (operational taxonomic units) were genera, Uhen (1999) added the taxon Nalacetus to leaving monophyly of more inclusive taxa to the matrix of O'Leary and Geisler (1999) be tested. Extant genera, which were used as and tested hypotheses concerning the strati- taxonomic exemplars in the molecular stud- graphic ®t of the most parsimonious trees ies of Gatesy (1998) and Gatesy et al. and the relative timing of the evolution of (1999a), were also included to facilitate a characters. Their most parsimonious trees are combined molecule and morphology phylo- identical to those of O'Leary and Geisler genetic analysis (Geisler, work in progress). (1999) except that Harpagolestes was the The selection of extinct taxa was based on sister group to Synoplotherium instead of simulation studies, which show that phylo- Mesonyx. genetic accuracy can be increased by break- ing up long branches, where branch length is INSTITUTIONAL ABBREVIATIONS the number of evolutionary events (Gray- AMNH-M Department of Mammalogy, Division beal, 1998; method 4 of Hillis, 1998). The of Vertebrate Zoology, American Mu- phylogeny of Artiodactyla and Cetacea likely seum of Natural History, New York contains long branches because many of the AMNH-VP Division of Paleontology (vertebrate branching events occurred in the Late Cre- collection only), American Museum taceous or Paleocene (O'Leary and Geisler, of Natural History, New York 1999). At least 89% of Artiodactyla, Cetacea, 2001 GEISLER: ARTIODACTYLA, CETACEA, MESONYCHIDAE 7 and close relatives are extinct (O'Leary and The ingroup for this study included 10 ce- Geisler, 1999); therefore, including extinct taceans, 9 mesonychids, 2 hapalodectids, 32 taxa for consideration greatly increases the artiodactyls, 4 perissodactyls (horses, rhinos, pool of taxa that likely attach near the bases tapirs), and 6 archaic ungulates (appendix 1). of long branches. In comparison to O'Leary and Geisler Several model-based studies have shown (1999), which is the most comprehensive that long branch attraction is a potential morphological analysis of artiodactyls and problem for phylogeny reconstruction using cetaceans to date, the present study includes parsimony, and that taxonomic sampling can 28 additional taxa. Leptictidae and Orycter- be used to reduce this problem. Felsenstein opus were included as outgroups and were (1978) demonstrated that, given a model of used to root all most parsimonious trees. The evolution that speci®es probabilities of stasis exclusion of Leptictidae from the ingroup or change between character states, phylog- was supported by Novacek (1986, 1992), and enies that have long terminal branches sep- Orycteropus was outside of the clade includ- arated by short internal branches will be in- ing artiodactyls and cetaceans in the most correctly reconstructed using parsimony. parsimonious trees of morphological studies Hendy and Penny (1989) suggested that this (Novacek, 1986, 1992; Gaudin et al., 1996; problem could be alleviated by adding taxa Shoshani and McKenna, 1998), molecule- that attach to the base of long branches. Their based analyses (Stanhope et al., 1996; Gatesy suggestion has been supported by the work et al., 1999b), and one combined analysis of Hillis (1998) and Graybeal (1998). (Liu and Miyamoto, 1999). Two carnivores Kim (1996) described apparently counter- (Canis and Vulpavus) and Rattus were added intuitive examples of phylogenies that led to to aid in a project that will integrate the cur- incorrect reconstructions using parsimony re- rent data set with previously published mo- gardless of the number and type of taxa sam- lecular data (Geisler, in prep.). Diacodexis is pled. His examples required that sampling be a critical but problematic early artiodactyl restricted to subtrees within the entire phy- taxon. It was split into two OTUs: Diacod- logeny, and he calculated the inconsistency exis pakistanensis and North American Was- using ®xed probabilities for estimating the atchian Diacodexis, with the latter being correct phylogeny of each subtree. Actual based primarily on specimens referred to D. studies are not restricted to sampling within metsiacus (Rose, 1985). The allocation of parts of the phylogeny, except possibly by species to Elomeryx follows MacDonald extinction or the absence of fossils; therefore, (1956), and the allocation of specimens to the probabilities of correctly estimating sub- Pakicetus follows Thewissen and Hussain trees depend on the sampling of taxa. Adding (1998). Most taxa were scored from speci- taxa that break up long branches can increase mens in the vertebrate paleontology and the probability of getting the wrong tree with mammalogy collections at the American Mu- parsimony if the branch lengths of the added seum of Natural History (appendix 1). taxa are longer than the original inconsistent branch (Kim, 1996). Both Kim (1996) and CHARACTER DATA Hulsenbeck (1991) showed that the converse is also true, that the inconsistency can be re- Each of the 68 ingroup and outgroup taxa moved if the added taxa have very short ter- were scored for the 186 morphological char- minal branches. Extinct taxa that are found acters listed in appendix 2, with codings for in strata near the age of speciation events of each taxon listed in appendix 3. Of the 186 interest (i.e., disputed nodes) are expected to morphological characters, approximately 47 have shorter branch lengths because ``they are original to this work, while the remaining had less time to evolve'' (Gauthier et al., characters are from previous morphological 1988: 193). Many of the taxa used in this studies (Webb and Taylor, 1980; Novacek, study are from the Paleocene and Eocene 1986; Janis and Scott, 1987; Gentry and (McKenna and Bell, 1997) and are close in Hooker, 1988; Scott and Janis, 1993; Thew- time to the estimated origin of the most ex- issen and Domning, 1992; Thewissen, 1994; clusive clade for which they are members. Geisler and Luo, 1998; O'Leary, 1998a; 8 AMERICAN MUSEUM NOVITATES NO. 40

O'Leary and Geisler, 1999; Luo and Ginger- 1936: pl. 2, ®gs. 2, 3); therefore, it is a po- ich, 1999). An attempt was made to include tential synapomorphy of Artiodactyla. In the all previously published morphological char- ruminants Bos and Ovis and in the suid Sus acters useful in determining whether or not the alisphenoid canal is absent and the infra- Cetacea belongs within the clade of living orbital ramus of the maxillary artery is lateral artiodactyls. Considering the diversity of to the alisphenoid (state 1) (Getty, 1975). taxa that belong within the ingroup, as well The alisphenoid canal is also absent in all as the volume of previous work on artiodac- extant cetaceans, and as in most artiodactyls tyl phylogeny, my goal was probably unre- the infraorbital ramus of the maxillary artery alistic; however, this matrix does provide a is lateral to the alisphenoid (Fraser and Pur- useful contribution for those wishing to purves, 1960). Absence of the alisphenoid canal sue this problem further. In comparsion to also occurs in the most basal cetaceans Pak- O'Leary and Geisler (1999), the present icetus and Ambulocetus; however, its absence study includes an additional 63 morphologi- in cetaceans may not be synapomorphic with cal characters. Subheadings within the char- the morphology of most artiodactyls because acter list in appendix 2 denote groups of the probable sister groups of Cetacea, the characters that occur in the same anatomical Mesonychidae and Hapalodectidae, have an region or share a common function. alisphenoid canal (Geisler and Luo, 1998). Character 96: P4 entocingulum.ÐPre- SELECTED CHARACTER DESCRIPTIONS sent, partially or completely surrounds the base of the protocone (0); absent or very Of the 186 morphological characters in small (1). If present, the entocingulum of P4 this study, I have selected 11 of them that are is on the lingual margin of the tooth. In the either potential synapomorphies of Artiodac- artiodactyl Elomeryx, P4 has an entocingulum tyla or synapomorphies of a more inclusive that begins at the parastyle, wraps around the mammalian clade. In cases where descrip- base of the protocone, and ends at the me- tions are insuf®cient, I have included illus- tastyle (state 0). The cingulum is separated trations. For additional descriptions of basi- from adjacent parts of the tooth by a deep cranial characters, see Geisler and Luo groove except for its lingualmost portion, (1998) and Luo and Gingerich (1999), and which is appressed to the base of the proto- for descriptions of dental characters, see cone (®g. 2A: en). Although most basal ar- Gentry and Hooker (1988) and O'Leary tiodactyls have a well-de®ned entocingulum, (1998a). it is absent in most extant artiodactyls in- Character 49: Alisphenoid canal (alar ca- cluding all ruminants except for Hypertra- nal).ÐPresent (0); absent (1) (Novacek, gulus, camelids, Sus, and Tayassu (state 1). 1986; Thewissen and Domning, 1992). The An entocingulum occurs on the P4 of the ear- alisphenoid canal transmits the infraorbital ly cetaceans Pakicetus and Georgiacetus, al- ramus of the maxillary artery (Wible, 1987; though it is absent in Basilosaurus. In con- Evans, 1993), and if the foramen rotundum trast to basal cetaceans, there is no entocin- opens into the medial wall of the alisphenoid gulum on the P4 of all mesonychids, such as canal, then the anterior half of the canal also Harpagolestes (®g. 2B) (state 1). carries the maxillary branch of the trigeminal Character 124: Occipital condyles.Ð nerve (Sisson, 1921; Evans, 1993). For the Broadly rounded in lateral view (0); V- group of taxa studied here, most of the prim- shaped in lateral view, in posterior view the itive taxa have an alisphenoid canal, includ- condyle is divided into a dorsal and a ventral ing Leptictidae, Eoconodon, Hyopsodus, half by a transverse ridge (1). The occipital Phenacodus, and Meniscotherium (state 0). condyles of many mammals, such as in Or- These observations are consistent with the ycteropus and Phenacodus, are smoothly view of Thewissen and Domning (1992) that convex and do not have a transverse ridge presence of the canal is primitive for Euthe- (state 0). By contrast, in most artiodactyls the ria. occipital condyle has a transverse ridge that The alisphenoid canal is absent in all ar- divides it into dorsal and ventral halves (state tiodactyls except for Cainotherium (HuÈrzeler, 1). The ridge begins at the lateral edge of the 2001 GEISLER: ARTIODACTYLA, CETACEA, MESONYCHIDAE 9

Fig. 2. Representative morphologies for the lingual margin of P4. Labial is toward the top of the page, anterior is to the left, and the scale bars represent 10 mm. A. The third and fourth upper premolars of the artiodactyl Elomeryx armatus (AMNH 582). Note the presence of a prominent entocingulum that nearly encircles the base of the protocone. An entocingulum on P4 is widely distributed among basal artiodactyl taxa; therefore, it is a potential synapomorphy of Artiodactyla. B. The third and fourth upper premolars of the mesonychid Harpagolestes orientalis (AMNH 26300). Note the complete absence of an entocingulum on P4. Abbreviations: en, entocingulum; P3, upper third premolar; P4, upper fourth premolar. condyle and stretches across its entire pos- because an entepicondylar foramen occurs in terior aspect. In lateral view the ridge gives most of the archaic taxa surveyed in this the condyle a V-shaped pro®le. The vertex of study, including Leptictidae, Orycteropus, the ``V'' is the top of the ridge, and in the Vulpavus, Arctocyon, Eoconodon, Hyopso- artiodactyl Poebrotherium the vertex points dus, Phenacodus, and Meniscotherium. The ventrally and slightly posteriorly (®g. 3: or). entepicondylar foramen is absent in all artio- The functional morphology of the ridge is dactyls, and thus its absence is a potential unknown; however, I suspect it works with synapomorphy of that group. It is also absent the alar and lateral atlanto-occipital liga- in all cetaceans, perissodactyls, the carnivore ments to temporarily lock the occipital/atlas Canis, and the rodent Rattus (state 1). joint in the position that most ef®ciently ori- Character 152: Third trochanter of femur ents the head for feeding. When the muscles (ordered).ÐPresent (0); highly reduced (1); that nod the head are relaxed, the morphol- absent (2) (Luckett and Hong, 1998; O'Leary ogy of the joint and the tension in the liga- and Geisler, 1999). The third trochanter is a ments would passively restore the head to its ¯ange that projects from the lateral side of former position. the humeral shaft. On average, it is situated Character 135: Entepicondylar fora- at one third of the distance from the proximal men.ÐPresent (0); absent (1) (Thewissen to the distal end of the humerus. The super- and Domning, 1992). The entepicondylar fo- ®cial gluteus muscle, which extends the ramen transmits the median nerve and the hindlimb at the hip joint (Evans, 1993), in- brachial artery, as in the carnivore Felis serts on the third trochanter. In ruminants, (Crouch, 1969). It is located on the distal end which lack a third trochanter, the super®cial of the humerus and perforates the proximal gluteus has fused with the biceps femoris to half of the medial epicondyle. Shoshani form a gluteobiceps. Instead of inserting on (1986) hypothesized that presence of an en- the femur, the gluteobiceps inserts on the cru- tepicondylar foramen was primitive for eu- ral facia, lateral patellar ligament, and facia therian mammals. His view is supported here lata (Getty, 1975). Presence of a large, 10 AMERICAN MUSEUM NOVITATES NO. 40

Fig. 3. Oblique posterolateral view of the right occipital condyle of Poebrotherium (AMNH 42257), with right and left stereopair views. The occipital condyle is divided into dorsal and ventral halves by a transverse ridge. The occipital ridge is a potential synapomorphy of Artiodactyla. Scale bar is 10 mm in length. Abbreviations: fm, foramen magnum; or, occipital ridge; tb, tympanic bulla. square-shaped third trochanter is probably 1947; O'Leary and Geisler, 1999). The most primitive for the ingroup because it is present widely recognized character that diagnoses in the outgroup taxon Orycteropus and the Artiodactyla is the double-pulleyed astraga- archaic taxa Arctocyon, Hyopsodus, Phena- lus (Schaeffer, 1947). The ``double-pulley'' codus, and Mesonychidae. refers to the fact that the proximal and distal The third trochanter is absent in all extant ends of the astragalus are deeply grooved, artiodactyls, and it is absent or very small in and that each end resembles a pulley. As in all extinct artiodactyls. Specimens of the bas- previous morphological studies (e.g., Thew- al artiodactyl Diacodexis from North Amer- issen and Domning, 1992; O'Leary and ica (Rose, 1985) and from Asia (Thewissen Geisler, 1999), the proximal and distal ends and Hussain, 1990) have a small rectangular of the astragalus are treated as independent ¯ange on the femur that is homologous to, characters. but smaller than, the third trochanter of Arc- The tibial articulation surface of the as- tocyon, Hyopsodus, perissodactyls, and other tragalus is divided into two parts: (1) a me- mammals. Thus, reduction of the third tro- dial part that faces medially or proximome- chanter is a potential synapomorphy of Ar- dially and articulates with the medial malle- tiodactyla, while complete loss of this struc- olus of the tibia, and (2) a lateral part that ture is a potential synapomorphy of a higher faces proximally and articulates with the rest level artiodactyl clade that includes the artio- of the tibia. It is the second part that becomes dactyl crown group. The archaic cetacean trochleated in many mammals. In the Creta- Ambulocetus has a third trochanter (Thewis- ceous eutherians Ukhaatherium (Horovitz, sen et al., 1996); therefore, its presence in 2000), Asioryctes (Kielan-Jaworowska, this taxon supports the exclusion of Cetacea 1977), and Protungulatum (Szalay and Deck- from the clade of all artiodactyls. er, 1974), the lateral part of the tibial articular Character 156: Proximal end of astraga- surface is slightly concave (state 0); there- lus (ordered).ÐNearly ¯at to slightly con- fore, a ¯at to slightly concave articulating cave (0); well grooved, but depth of trochlea surface on the astragalus for the tibia is prob- Ͻ25% its width (1); deeply grooved, depth ably primitive for Eutheria. In the outgroups Ͼ30% its width (2) (derived from Schaeffer, Orycteropus and Leptictidae and the ungu- 2001 GEISLER: ARTIODACTYLA, CETACEA, MESONYCHIDAE 11 late mammals Eoconodon, Pachyaena (®g. 5A), as in all other artiodactyls (Schaeffer, 4b), Mesonyx, and Phenacodus (®g. 4C: tr), 1947). Many other mammals, including all the tibial articulation surface on the astraga- perissodactyls, Canis, Rattus, and the meson- lus is well grooved. In these taxa, the maxi- ychids Mesonyx and Synoplotherium (Wort- mum depth of the tibial articulation surface man, 1901), also lack an astragalar foramen. is less than 25% the transverse width of the By contrast, the astragalar foramen is present trochlea, where trochlear width is measured in many archaic ungulates, including Hyop- between the medial and lateral parasagittal sodus, Phenacodus, Meniscotherium, Pach- ridges of the tibial articulation surface (®g. yaena, Dissacus, Arctocyon, Eoconodon, and 4: ltr, mtr) (state 1). The early cetacean Am- Orycteropus. In Pachyaena and Phenacodus, bulocetus was also scored ``1'' for this char- the astragalar foramen is clearly visible in acter because it has a relative trochlear depth dorsal view (®g. 4B, C: af) (state 0). of 19% (Thewissen, 1994). Thewissen et al. (1996) noted that the ear- In nearly all artiodactyls, the trochlea is ly cetacean Ambulocetus has an astragalar fo- deeply grooved with its depth greater than ramen; therefore, this character supports the 30% its width (state 2). The entire trochlea exclusion of Cetacea from Artiodactyla is convex along the sagittal plane but is con- (Luckett and Hong, 1998). Thewissen et al. cave in the transverse plane, thus it is shaped (1998) and Thewissen and Madar (1999) de- like a pulley (®g. 4A: tr). A deeply grooved scribed several astragali that they referred to trochlea is a potential synapomorphy of Ar- Cetacea; however, they did not mention tiodactyla; however, a few artiodactyls are whether the astragalar foramen was present coded ``1'' for this character. The proximal or absent. end of the astragalus is only slightly grooved Character 159: Distal end of astragalus in the artiodactyls Homacodon, Merycoido- contacts cuboid (ordered).ÐContact absent don, Leptoreodon, and Hexaprotodon (state (0); contact present, articulating facet on as- 1). The trochlea of perissodactyls is deeply tragalus forms a steep angle with a parasag- grooved like most artiodactyls (state 2); how- ittal plane (1); contact present and large, fac- ever, this morphology is probably convergent et almost forms a right angle with a parasag- because in the stem taxa to Perissodactyla ittal plane (2). In the outgroup Orycteropus (e.g., Meniscotherium, Phenacodus) the as well as other taxa, including Rattus, Vul- trochlea is slightly grooved (®g. 4C: tr). pavus, Canis, Hyopsodus, Phenacodus, and Character 157: Astragalar canal.ÐPre- Meniscotherium, there is no contact between sent (0); absent (1) (Shoshani, 1986). The as- the cuboid and the astragalus. In these taxa, tragalar canal perforates the proximal end of the head of the astragalus only contacts the the astragalus. The proximal entrance of the navicular. In mesonychids such as Dissacus canal, known as the astragalar foramen, is and Pachyaena (®gs. 4, 5: cuf), the lateral within or slightly plantar to the lateral tibial side of the head of the astragalus bears a fac- articulation surface, while the plantar end of et for the cuboid (state 1). The long axis of the canal leads into the interarticular sulcus. the facet is oriented anterolateral to postero- Although the occupant, if any, of the astrag- medial. In mesonychids little of the body alar canal is not known (Schaeffer, 1947), the weight bore by the astragalus could be trans- interarticular sulcus is a point of attachment ferred to the cuboid because their contact for the interosseous ligament between the as- surfaces are oriented vertically, not trans- tragalus and calcaneus (Sisson, 1921). versely. The astragalar foramen is absent in all ar- The astragali of all artiodactyls have very tiodactyls, and previous authors have stated large cuboid facets, as is seen in Archaeoth- that its absence is a synapomorphy of this erium (®g. 4A: cuf). The cuboid facet is ori- group (Geisler and Luo, 1998; Luckett and ented nearly perpendicular to the sagittal Hong, 1998). As can be seen in Archaeoth- plane, thus facing distally (state 2). A large erium, the trochlea of the astragalus is not distally facing astragalus occurs in all artio- perforated by an astragalar foramen (®g. 4A) dactyls; therefore, it is a potential synapo- (state 1). In addition, the interarticular sulcus morphy of that group. The size and orienta- is completely absent in Archaeotherium (®g. tion of the cuboid facet in artiodactyls is al- 12 AMERICAN MUSEUM NOVITATES NO. 40 2001 GEISLER: ARTIODACTYLA, CETACEA, MESONYCHIDAE 13

most certainly related to distributing body weight between the third and fourth digits. The weight transferred from the astragalus to the cuboid would be passed onto the fourth digit, which is expected in a paraxonic pes such as that which occurs in all artiodactyls (Schaeffer, 1947). Paraxony of the foot and the size of the astragalus/cuboid contact are at best only partially dependent on each other because mesonychids have a paraxonic pes but only a small cuboid/astragalar contact; therefore, these characters are treated inde- pendently in the phylogenetic analysis. Although the cuboid of early cetaceans is not known, the morphology of the putative cetacean astragali described by Thewissen et al. (1998) and Thewissen and Madar (1999) suggests that the cuboid did not contact the astragalus in these taxa. In H-GSP 97227 the neck and head of the astragalus are directed distomedially, away from the cuboid. If the cuboid was similar in size to that of mesonychids or artiodactyls, then the astragalus would not contact the cuboid. However, if the cuboid was transversely expanded, then contact was possible. Character 162: Lateral process of astragalus.ÐPresent, ectal facet of the astragalus faces in the plantar direction and its distal

← Fig. 4. Dorsal views of the right astragali of three ungulates. Line drawings are on page facing the stereopairs. Lateral is to the left, proximal is toward the top of the page, and the scale represent 10 mm. A. Right astragalus of the artiodactyl Ar- chaeotherium sp. (AMNH 1277). Note the deeply grooved trochlea, absence of the lateral process, and the large cuboid facet that faces distally. This view is more accurately described as anterior because of the digitigrade posture of all artiodactyls. B. Right astragalus of the mesonychid Pachyaena ossifraga (AMNH 16154). The astragalus of Pachyaena has an astragalar foramen, a lateral process (broken in this specimen), and a small, distolaterally facing cuboid facet. C. Left astragalus (photos reversed for comparison) of Phena- codus sp. (AMNH 15262). Note the pronounced lateral process. Abbreviations: af, astragalar foramen; an, astragalar neck; cuf, articular facet for the cuboid; lp, lateral process; ltr, lateral trochlear ridge; mtr, medial trochlear ridge; naf, articular facet for the navicular; tr, trochlea (which is also the lateral part of the tibial articular surface). 14 AMERICAN MUSEUM NOVITATES NO. 40 2001 GEISLER: ARTIODACTYLA, CETACEA, MESONYCHIDAE 15

end points laterally (0); absent, ectal facet faces laterally and its long axis is parasagittal (1) (Schaeffer, 1947). The plantar face of the lateral process bears the lateral half of the ectal facet, which articulates with the lateral astragalar facet of the calcaneus. The presence or absence of the lateral process is correlated to the orientation of the ectal facet of the astragalus. If the ectal facet is oriented proximomedial to distolateral, then its distal end juts outward from the lateral side of the astragalus forming the lateral process. If the ectal facet is parasagittal in orientation, then the lateral process is absent. Schaeffer (1947) discussed the differences between the ectal facets of artiodactyls and archaic ungulates. Later, Geisler and Luo (1998) and then Thewissen and Madar (1999) used the morphology of the lateral process or ectal facet as a character for cladistic analysis. Although these authors emphasized different aspects of astragalar morphology, they are considered here to represent interdependent changes of the same morphological region. In Phenacodus the ectal facet is very large and equal in width to the sustentacular facet. The ectal facet faces in the plantar direction and its long axis is oriented proximomedial

← Fig. 5. Plantar views of the right astragali of three ungulates. Line drawings are on page facing the stereopairs. Lateral is to the right, proximal is toward the top of the page, and the scale bars represent 10 mm. A. Plantar view of the right astragalus of the artiodactyl Archaeotherium sp. (AMNH 1277). Note the wide and laterally positioned sustentacular facet, absence of the interarticular sulcus, and the laterally facing ectal facet. B. Right astragalus of the mesonychid Pachyaena ossifraga (AMNH 16154). The astragalus of Pachyaena has a small and medially positioned sustentacular facet, an astragalar canal leading into an interarticular sulcus, and a large plantar- facing ectal facet. C. Left astragalus (photos reversed for comparison) of Phenacodus sp. (AMNH 15262). The astragalus of Phenacodus is very similar to that of Pachyaena except for an occluded astragalar canal and the absence of an articular facet with the cuboid. Abbreviations: ac, astragalar canal; cuf, articular facet for the cuboid; ecf, ectal facet; ins, interarticular sulcus; naf, articular facet for the navicular; suf, sustentacular facet. 16 AMERICAN MUSEUM NOVITATES NO. 40 to distolateral (®g. 5C: ecf). In association all artiodactyls. Geisler and Luo (1998) de- with the orientation of the ectal facet, the as- veloped a cladistic character for the relative tragalus bears a stout, triangular-shaped lat- size of facet. They described state ``0'' as eral process (®g. 4C: lp) (state 0). The lateral having a sustentacular width that is less than side of the astragalus proximal to the lateral 40% the width of the astragalus and state process is occupied by the articular surface ``1'' as having a sustentacular width greater for the lateral malleous of the ®bula. The dis- than 70% that width. O'Leary and Geisler tal end of the ®bular facet extends onto the (1999) used a similar character description lateral process, and it is twisted, relative to except that state ``0'' was described as being more proximal portions, so that it faces dor- less than 50% the astragalar width. sally instead of laterally. Based on post-mor- Although not mentioned, Geisler and Luo tem articulation of the tibia, ®bula, and as- (1998) and O'Leary and Geisler (1999) mea- tragalus in Phenacodus and Pachyaena, it sured astragalar width across the trochlea at appears that the lateral process in archaic un- a position proximal to the base of the lateral gulates forms a stop to dorsal ¯exion at the process. In reviewing the coding for this proximal ankle joint. Another probable func- character, I came upon several discrepancies. tion of the lateral process/ectal facet complex For example, both Pachyaena and Phena- is in transferring weight from the astragalus codus, scored as ``0'' in both studies, actually to the calcaneus. When the lateral process is fall between states ``0'' and ``1'' with sus- present, the ectal facet is perpendicular to the tentacular widths of 57% and 65%, respec- long axes of the tibia and ®bula and thus can tively (®g. 5B, C: suf). Despite the similarity ef®ciently pass weight onto the calcaneus. in size between the sustentacular facets of In all artiodactyls, including Diacodexis Phenacodus and Pachyaena and the susten- and Archaeotherium (®gs. 4A, 5A), the lat- tacular facets of artiodactyls, there are clear eral process of the astragalus is absent (state qualitative differences between them. I im- 1). Unlike Phenacodus, the ectal facet in ar- proved this character by emphasizing the po- tiodactyls is parasagittal and faces laterally, sition of the lateral margin of the sustentac- instead of in the plantar direction (®g. 5A: ular facet, instead of its relative width. ecf). It is fairly small and could not transfer In the primitive condition, as represented weight to the astragalus because it is parallel, by Pachyaena and Phenacodus (®g. 5B, C: not perpendicular, to the long axes of the tib- suf), the lateral margin of the sustentacular ia and ®bula. The proximal end of the ectal facet is well medial to the lateral edge of the facet in Archaeotherium does jut outward trochlea (state 0). In Pachyaena ossifraga, from the lateral surface of the astragalus; the sustentacular facet is kidney-shaped, with however, this small protrusion is not homol- the long axis of the facet oriented proximo- ogous to the lateral process because it is ad- laterally to distomedially (®g. 5B: suf). The jacent to the proximal, not the distal, end of sustentacular facet occupies approximately the ectal facet. 30% of the plantar surface, and the rest of Character 163: Sustentacular facet of the the plantar surface includes a large interar- astragalus.ÐNarrow and medially posi- ticular sulcus between the sustentacular and tioned, lateral margin of sustentacular facet ectal facets and a broad rugose region be- of the astragalus well medial to the lateral tween the sustentacular facet and the astrag- margin of the trochlea (0); wide and laterally alar head. positioned, lateral margin in line with the lat- In artiodactyls, such as Archaeotherium eral margin of the trochlea (1) (derived from (®g. 5A: suf), the sustentacular facet is wide Schaeffer, 1947; Geisler and Luo, 1998). The and is placed such that its lateral margin is sustentacular facet of the astragalus is the ar- in line with the lateral edge of the trochlea. ticular surface on the plantar side that artic- Much of the apparent increase in size of the ulates with the sustentaculum of the calca- sustentacular facet is caused by the lateral neus. It is usually centered on the plantar position. In the primitive condition, the sus- face and is situated medial to the ectal facet. tentacular facet is medial to the anterior face Schaeffer (1947) was the ®rst to note that a of the astragalar neck; therefore, a cross sec- large sustentacular facet is characteristic of tion through the astragalar neck is rhomboi- 2001 GEISLER: ARTIODACTYLA, CETACEA, MESONYCHIDAE 17 dal, with much of the lateral surface visible gy of these astragali can be described in in plantar view and much of the medial sur- terms of the characters used in this study. face visible in dorsal view. The sustentacular The sustentacular facet of H-GSP 97227, a facet appears small because the lateral sur- putative pakicetid astragalus, is very differ- face is visible in plantar view. In artiodactyls ent from those of artiodactyls. Like Pach- the sustentacular facet is directly plantar to yaena and other archaic ungulates, the lateral the trochlea; therefore, a cross section margin of the sustentacular facet is far me- through the astragalus is approximately dial to the lateral edge of the trochlea. Unlike square-shaped. The lateral surface of the as- artiodactyls, the proximolateral corner is not tragalus is not visible in plantar view, creat- expanded; however, it is unclear if the inter- ing the appearance of a large sustentacular articular sulcus was present. I suspect it was facet. because the cetacean Ambulocetus has an as- In addition to a far lateral position, the tragalar foramen (Thewissen et al., 1996), long axis of the artiodactyl sustentacular fac- and in all ungulate astragali I have examined et is aligned longitudinally, and thus parallel the astragalar foramen and the interarticular to the medial and lateral edges of the troch- sulcus always coexist. lea. This contrasts with the primitive condi- Character 165: Articulation of calcaneus tion as exempli®ed by Pachyaena, where the and cuboid.ÐFlat, proximal articulating sur- long axis of the sustentacular facet is orient- face of the cuboid in one plane and corre- ed proximolaterally to distomedially (®g. 5B: sponding surface of the calcaneus faces dis- suf). To transform the orientation of the sus- tally (0); sharply angled and curved, proxi- tentacular facet from the primitive condition mal surface of the cuboid has a distinct step to the artiodactyl morphology requires a between the facets for the calcaneus and as- counterclockwise (on the right astragalus) ro- tragalus (1). Although Schaeffer (1947) was tation of 30Њ to 40Њ. The rotation in artiodac- the ®rst to recognize the unique morphology tyls coincides with expansion of the proxi- of the calcaneus/cuboid contact of artiodac- molateral corner of the sustentacular facet tyls, Thewissen and Madar (1999) were the and absence of the interarticular sulcus (®g. ®rst to reformulate the character for cladistic 5A). The orientation of the sustentacular fac- analysis. Although Thewissen and Madar et was not coded separately from its position (1999) stressed the transverse widths of the because I think it is related to character 159, articulation surfaces, I stress the angle and which codes for the size and orientation of curvature of the facets because they are com- the cuboid facet. A large cuboid facet occurs mon to all artiodactyls but do not occur in when the head of the astragalus is in a lateral any other mammal. The cuboid's articulation position, directly distal to the trochlea. A lat- facet for the calcaneus in the artiodactyl Dia- eral position of the astragalar head aligns the codexis (AMNH 27787) is fairly wide; there- proximal and distal articulating facets of the fore, a narrow facet does not characterize all astragalus, and the long axis of the susten- artiodactyls. tacular facet predictably stretches between In the basal eutherian Ukhaatherium, the the proximal and distal ends along a para- cuboid facet of the calcaneus faces primarily sagittal line. distally, with a slight medial component (Ho- Thewissen et al. (1998) and Thewissen rovitz, 2000), and a similar morphology oc- and Madar (1999) described astragali that curs in the basal ungulate Protungulatum they assigned to the basal cetacean families (Szalay and Decker, 1974). Thus, the prob- Ambulocetidae and Pakicetidae. Following able primitive condition for Eutheria is a cu- the reasons of O'Leary and Geisler (1999), boid facet that faces distally or distomedially the morphology of these bones was not con- (state 0). The primitive morphology of the sidered in scoring characters of the hindlimb. calcaneus/cuboid joint is exempli®ed by the Although I do not reject the allocation of mesonychid Pachyaena (®g. 6B: caf). The these isolated elements to Cetacea, I consider articular surface on the cuboid for the cal- the association to be too weak to justify in- caneus is nearly ¯at and approximately tri- cluding these data in the phylogenetic anal- angular in shape. Lateral to the articular sur- ysis. Despite this uncertainty, the morpholo- face for the calcaneus is a rectangular con- 18 AMERICAN MUSEUM NOVITATES NO. 40

Fig. 6. Proximal views of the cuboids of Archaeotherium and Pachyaena, with right and left stereopair views. Plantar is toward the top of the page, lateral is to the left, and the scale bars represent 10 mm. A. Right cuboid of the artiodactyl Archaeotherium (AMNH 1277). Note the distinct step between the articular facets for the astragalus and cuboid, a morphology common to all artiodactyls. B. Right cuboid of Pachyaena ossifraga (AMNH 16154). Note the wide articular facet for the cuboid. Abbre- viations: asf, articular facet for the astragalus; caf, articular facet for the calcaneus. cave facet for the astragalus (®g. 6B: asf). rowness of the joint is correlated with the Both the calcaneus facet and the astragalar degree of alignment of the astragalar head, a facet of the cuboid are nearly in the same character not included because of its proba- plane transverse plane (®g. 7B), and the ble interdependence with this and other ankle joints between the cuboid and the astragalus characters. Near or total longitudinal align- and calcaneus are collectively referred to as ment of the astragalar head with the trochlea the lower tarsal joint. During movement at of the astragalus is correlated with a large the lower tarsal joint, the tuber of the cal- cuboid/astragalus contact, and consequently caneus would have maintained a similar an- with a narrower calcaneus/cuboid contact. gle with the pes because the joint surface is The correlation is not perfect, as is shown by fairly ¯at. Diacodexis (AMNH 27877). In this speci- In nearly all artiodactyls the articulation men, the calcaneus facet on the cuboid is still between the calcaneus and the cuboid is large even though the cuboid has substantial transversely narrow (®g. 6A: caf). The nar- contact with the astragalus. The calcaneus 2001 GEISLER: ARTIODACTYLA, CETACEA, MESONYCHIDAE 19

Fig. 7. Dorsal views of the right ankles of two ungulates. Lateral is to the left, proximal is toward the top of the page, and the scale bars represent 10 mm. Arrows indicate the dorsal edge of the cuboid's articular facet for the calcaneus. A. Ankle of Archaeotherium (AMNH 1277). Note the distinct step between the articulation of the cuboid with the calcaneus and its articulation with the astragalus. The calcaneus will move farther down the face of the cuboid during dorsal ¯exion. B. Ankle of Pachyaena ossifraga (AMNH 16154). Note that the cuboid articulates with the calcaneus and the astragalus in nearly the same transverse plane. Abbreviations: ast, astragalus; cal, calcaneus; cub, cuboid. facet is wide and its lateral edge overhangs for the astragalus. The cuboid's facet for the more distal parts of the cuboid. calcaneus is convex parasagittally, while its The cuboid of artiodactyls can be distin- facet for the astragalus is concave parasagi- guished from all other mammals because tally (®g. 6A). The curve in the calcaneus there is a pronounced step between the dorsal facet is largely formed by a distal turn near (anterior if digitigrade) edges of the cuboid the dorsal edge of the facet, which accentu- articulation surfaces for the astragalus and ates the step between the cuboid and astrag- calcaneus (®gs. 6A, 7A). The articulating alar facets. In addition, the neck of the as- facet for the astragalus is more proximal than tragalus in artiodactyls appears to be shorter that for the calcaneus. Two factors apparently than those of archaic ungulates; therefore, the contribute to the formation of the step: (1) astragalar facet on the cuboid is in a more the convexity of the articulating surface with proximal position. the calcaneus, and (2) a relatively short neck According to Schaeffer (1947), the angle 20 AMERICAN MUSEUM NOVITATES NO. 40 between the calcaneus and the pes in artio- equivocal synapomorphies, as indicated in dactyls changes during movement at the low- this analysis, have previously been suggested er tarsal joint, thus indicating rotation be- as synapomorphies of the same clade. The tween the cuboid and calcaneus. The axis of term ``unequivocal'', as used here, means rotation for movement at the calcaneus/cu- that the character change occurs at a speci®c boid joint is nearly transverse, perpendicular node in all most parsimonious trees under all to the lateral side of the cuboid, and passes most parsimonious optimizations. through the proximal end of the cuboid and Previous phylogenetic hypotheses were the distal end of the astragalus. To maintain tested with the morphological matrix of this continual contact between the calcaneus and study by calculating their minimal tree cuboid during movement at the lower tarsal lengths. Many of the taxa that are included joint, the astragalus and calcaneus must here were not included by previous authors. move simultaneously in the same direction. Newly added taxa were incorporated into This suggests that the curved cuboid/calca- their hypotheses by using a backbone phy- neus articulation allows for a larger amount logenetic constraint, which when enforced in of rotation between the astragalus and the na- a search places taxa that are excluded from vicular than in taxa that have a ¯at calcaneus/ the constraint de®nition so that the overall cuboid articulation. The amount of rotation tree length is minimized (Swofford and Be- is not directly proportional, with the astrag- gle, 1993). Constraint trees were constructed alus rotating much more than the calcaneus. in MacClade 3.01 and then implemented in PAUP 3.1.1 by saving the shortest trees that PHYLOGENETIC ANALYSES AND OPTIMIZATIONS were compatible with the constraint. The length of the unconstrained most parsimoni- Parsimony-based cladistic methods were ous trees was subtracted from the length of used for phylogeny reconstruction, resulting the shortest trees from the constrained anal- in phylogenetic hypotheses that maximize yses to calculate the degree, measured in explanatory power (Farris, 1983). MacClade number of steps, that the current matrix con- 3.01 (Maddison and Maddison, 1992) was tradicts alternative phylogenetic hypotheses. used for entering and editing the morphological matrix, and NONA 1.9 (Goloboff, 1994) BRANCH SUPPORT and PAUP 3.1.1 (Swofford, 1993) were used for ®nding the most parsimonious (MP) Branch support (Bremer, 1988, 1994) was trees. Tree searches with PAUP were heuris- determined by combining the results of sev- tic with the following parameters: TBR (tree eral separate analyses. The ®rst analysis used bisection and reconnection) branch swap- extensive swapping on trees found by 100 ping, hold 1 tree at each step, save no more random addition searches, as implemented in than 10 suboptimal trees for each replicate, NONA (Goloboff, 1994). More than 100,000 and random stepwise addition of taxa with trees were found within 10 steps of the op- 1000 replications. Two separate searches timal length. Strict consensus trees for all with NONA were performed with the follow- trees less than a speci®c length were con- ing commands: (1) hold/10 and mult*1000; structed to determine the branch-support val- (2) nix* 10000, with the starting tree from ues for each clade. Available computer mem- the ®rst analysis. The ®rst analysis is com- ory ®lled before all branch swapping was parable to that of PAUP, and the second uses performed on all trees; therefore, I suspect the parsimony ratchet, a method of reweight- that some of the initial branch-support values ing characters to explore different tree is- were overestimated. To improve the estimate, lands (Nixon, 1999). Comparisons between two additional tree searches using the parsi- different optimizations and tree-length cal- mony ratchet (Nixon, 1999), as implemented culations for alternative topologies were per- in NONA, were used to ®rst ®nd all trees that formed using MacClade 3.01 (Maddison and were one step longer and then all trees that Maddison, 1992). Unequivocal synapomor- were two steps longer. Swapping was per- phies were derived using the apo/ command formed on all trees before the memory ®lled; in NONA. Citations are provided where un- therefore, nodes with branch-support values 2001 GEISLER: ARTIODACTYLA, CETACEA, MESONYCHIDAE 21 reported in ®gure 8 of 1 or 2 are thought to odontia, Ruminantia, Cameloidea (Cameli- be accurate. dae ϩ Oromerycidae), Camelidae, Xipho- The branch-support values greater than 2 dontoidea, and Cetacea (®gs. 8, 9). Suina were checked with PAUP (Swofford, 1993) (Suidae ϩ Tayassuidae) and Suoidea (Suina by ®nding the shortest trees that are not com- ϩ Hippopotamidae) are monophyletic only if patible with a constraint tree, where the con- Perchoerus, which has been considered a straint speci®es one node in the strict con- basal peccary, is excluded from both groups. sensus of the most parsimonious trees. Con- Phenacodus and Meniscotherium are succes- straint trees, command ®les, and output ®les sive sister groups to Perissodactyla in all were generated using the program TreeRot most parsimonious trees, as suggested by (Sorenson, 1996). The command ®le gener- previous authors (Gregory, 1910; Radinsky, ated by TreeRot was modi®ed so that 100 1966; Van Valen, 1978; Thewissen and heuristic replicates were performed for each Domning, 1992; Geisler and Luo, 1998; node and only 20 suboptimal trees were held O'Leary and Geisler, 1999). for each replicate. The lowest branch-support A monophyletic Artiodactyla (®g. 8: taxon value over all analyses was chosen as the ®- A) was found in all most parsimonious trees nal estimate. This multiple-step approach re- and has a branch support of two. Monophyly sulted in a decrease in one to three steps for of Artiodactyla is breached in trees three branch support values of several nodes, as steps longer by the inclusion of Perissodac- compared to the initial estimate from the tyla, but not Cetacea, into the clade including 100,000 saved trees. Bootstrapping was not all artiodactyls. Four unequivocal synapo- used as a measure of character-based nodal morphies support Artiodactyla, including support because it violates the basic assump- characters 36 (2 → 1), a short mastoid pro- tions of the method when applied to char- cess of the petrosal; 49 (1 → 0), absence of acter data (Kluge and Wolf, 1993; Carpenter, alisphenoid canal (O'Leary and Geisler, 1996). The character matrix used in this 1999); 96 (0 → 1), presence of an entocin- study is not a random sample of characters, gulum on P4 (®g. 2A: en); and 124 (0 → 1), but was compiled by focusing on characters presence of a transverse ridge of the occipital relevant to the higher level phylogeny of Ar- condyle dividing it into dorsal and ventral tiodactyla, Cetacea, and Mesonychidae. halves (®g. 3: or). Several characters that have been considered as synapomorphies of RESULTS Artiodactyla are equivocal when optimized onto these trees because Andrewsarchus, a ALL TAXA poorly known taxon that is coded for only When all ingroup and outgroup taxa were 39% of the characters, is positioned as its included, both PAUP and NONA found 32 sister group. The following characters are most parsimonious trees that were 1635 steps synapomorphies of Artiodactyla under de- long. When all polymorphism was interpret- layed optimization or for Artiodactyla ϩ An- ed as uncertainty, the tree length was 1412 drewsarchus under accelerated optimization: steps. The default in NONA reported 22 characters 135 (0 → 1), absence of entepi- trees, but 32 trees were found when the condylar foramen of the humerus; 152 (0 → ambϭ command was used. The difference 1), reduced third trochanter of the femur relates to how the programs deal with zero- (Luckett and Hong, 1998; O'Leary and Geis- length branches, as discussed by Coddington ler, 1999); 156 (1 → 2), deeply grooved, tib- and Scharff (1994). When using the parsi- ial articular surface of the astragalus (Schaef- mony ratchet (Nixon, 1998), as implemented fer, 1947); 157 (1 → 0), absence of the as- in NONA, the same 32 shortest tree were tragalar canal (Luckett and Hong, 1998; found in over 60% of 10,000 iterations. A Geisler and Luo, 1998); 159 (1 → 2), astrag- strict consensus of the 32 most parsimonious alar contact with cuboid large and oriented trees includes a monophyletic Perissodactyla, nearly perpendicular to the sagittal plane; Artiodactyla, Paraxonia (Artiodactyla ϩ Ce- 162 (0 → 1), absence of lateral process of tacea ϩ Mesonychidae ϩ Hapalodectidae), astragalus (Schaeffer, 1947; O'Leary and Hippopotamidae, Oreodontoidea, Neoselen- Geisler, 1999; Thewissen and Madar, 1999); 22 AMERICAN MUSEUM NOVITATES NO. 40 2001 GEISLER: ARTIODACTYLA, CETACEA, MESONYCHIDAE 23

Fig. 9. The phylogeny within Artiodactyla, enlarged from the strict consensus shown in ®gure 8. Ruminantia is monophyletic in all most parsimonious trees as well as the superfamilies or families Cameloidea, Camelidae, Oreodontoidea, Protoceratidae, and Hippopotamidae. Taxon abbreviations: CA, Cameloidea; H, Hippopotamidae; L, Camelidae; N, Neoselenodontia; O, Oreodontoidea; R, Ruminantia; ``S'', Suina, which is paraphyletic because it excludes Perchoerus; T, Protoceratidae; U, Suiformes.

163 (0 → 1), laterally positioned sustentac- and 175 (0 → 1), long third metatarsal. Ab- ular facet (Schaeffer, 1947; Geisler and Luo, sence of the alisphenoid canal (Geisler and 1998; Thewissen and Madar, 1999; O'Leary Luo, 1998) and probably absence of the lat- and Geisler, 1999); 165 (0 → 1), transversely eral process of the astragalus (Thewissen et narrow and sharply angled cuboid/calcaneus al., 1998; Thewissen and Madar, 1999) also articulation (Thewissen and Madar, 1999); occur in cetaceans.

← Fig. 8. Strict consensus of 32 most parsimonious trees for the morphological data listed in appendix 3. Each most parsimonious tree is 1635 steps long (polymorphisms included as steps), has a consistency index of 0.31, and has a retention index of 0.60. Branch-support values are immediately above and to the left of their respective nodes. Artiodactyla, Neoselenodontia, and Suiformes are monophyletic in all shortest trees. Taxon abbreviations: A, Artiodactyla; C, Cetacea; N, Neoselenodontia, P, Perissodactyla; R, Acreodi; U, Suiformes; X, Paraxonia. 24 AMERICAN MUSEUM NOVITATES NO. 40

Several characters previously suggested as lier studies that found a closer phylogenetic synapomorphies of Artiodactyla are consid- relationship between Cetacea and Perisso- ered equivocal synapomorphies in this anal- dactyla (Novacek, 1986; Novacek and Wyss, ysis because they may support other nodes, 1986; Prothero et al., 1988; Thewissen, and others are precluded from being artio- 1994). Paraxonia has a branch support of dactyl synapomorphies because of their ab- only one but is supported by several postcra- sence in many basal artiodactyls. An en- nial characters, including characters 139 (0 larged lacrimal (states 3 and 4 of character → 2), posterior edge of ulna concave; 141 (0 60) is not a synapomorphy of Artiodactyla, → 3), proximal end of radius split into three as suggested by Prothero (1993), because the articulation surfaces; 142 (0 → 1), distal ra- lacrimal is small, relative to the orbit, in Dia- dius split into scaphoid and lunate fossae; codexis pakistanensis, Gobiohyus, Mixtoth- 158 (0 → 1), saddle-shaped navicular artic- erium, Cebochoerus, camels, basal rumi- ulation surface on the astragalus (O'Leary nants, Cainotherium, and Agriochoerus. and Geisler, 1999); and 179 (0 → 1), ventral Based on the most parsimonious trees for the edge of distal phalanges ¯at (O'Leary and morphological data described here, an en- Geisler, 1999). Three characters listed by larged lacrimal is interpreted to have evolved Geisler and Luo (1998) as unequivocal syn- twice, being a synapomorphy of Suiformes apomorphies of Paraxonia are here consid- (®gs. 8, 9: taxon U) and of the clade includ- ered equivocal: reduced entepicondyle of hu- ing Tragulus, Ovis, Bos, and Odocoileus. An merus, three primary bronchi of the lungs, enlarged orbitosphenoid separating the fron- and sparse cavernous tissue of the penis. As tal and alisphenoid was also mentioned by the name Paraxonia implies, a paraxonic Prothero (1993) as an artiodactyl synapo- hindlimb has been previously considered a morphy (character 51); however, the alisphe- potential synapomorphy of this clade (Thew- noid contacts the frontal in Diacodexis pak- issen, 1994; Geisler and Luo, 1998); how- istanensis, Entelodontidae, and Perchoerus. ever, this character state is here optimized as Separation of the frontal and alisphenoid by a synapomorphy of a more inclusive group the orbitosphenoid is instead interpreted as a that includes Arctocyon and carnivores. Ca- synapomorphy of a subclade of artiodactyls nis clearly has a paraxonic pes (Evans, 1993: that includes Bunomeryx, Oreodontoidea, ®g. 10±115), and Vulpavus (AMNH 12626) and Neoselenodontia. A trochleated distal ar- has a slightly paraxonic pes comparable to ticular surface for the navicular on the as- the condition seen in mesonychids (O'Leary tragalus has been suggested as an artiodactyl and Rose, 1995b). synapomorphy (Schaeffer, 1947); however, All of the most parsimonious trees include the surface in Diacodexis is slightly grooved, several clades of suiform artiodactyls that similar to the degree seen in perissodactyls contradict the molecule-based phylogenies and mesonychids. A trilobed dP4 is a syna- that place Hippopotamidae as a close relative pomorphy of the crown group of artiodactyls of ruminants and cetaceans. Suiformes (®gs. and possibly of the entire group (Gentry and 8, 9: taxon U), here de®ned as Hippopotam- Hooker, 1988; Luckett and Hong, 1998). idae ϩ Suidae ϩ Tayassuidae ϩ Entelodon- Diacodexis and Homacodon are scored as tidae ϩ Anthracotheriidae, has a branch sup- ``?'' for this character; however, a potentially port of three and is diagnosed by 11 unequiv- homologous and early stage of this mor- ocal synapomorphies: characters 2 (0 → 1), phology has been reported in some speci- absence of sulcus on promontorium for the mens of Diacodexis (Luckett and Hong, internal carotid artery; 7 (0 → 1), small post- 1998). glenoid foramen; 8 (0 → 1), postglenoid fo- Paraxonia (®g. 8: taxon X), a clade in- ramen in petrosal/squamosal suture; 11 (0 → cluding Artiodactyla and Cetacea to the ex- 1), absence of subarcuate fossa of the petro- clusion of Perissodactyla, was present in all sal; 36 (1 → 0), absence of mastoid process most parsimonious trees. This result is con- of the petrosal; 40 (0 → 2 or 3), external sistent with recent parsimony-based morpho- auditory meatus of intermediate length or logical analyses (Geisler and Luo, 1998; long; 60 (1 → 2 or 3), lacrimal exposure on O'Leary and Geisler, 1999) but is unlike ear- face moderate or large; 64 (0 → 1), elongate 2001 GEISLER: ARTIODACTYLA, CETACEA, MESONYCHIDAE 25 face; 73 (0 → 1), angle of mandible forms a ϩ Cetacea) has a branch support of one (®g. ventral ¯ange; 91 (0 → 1), P1 with two roots; 8: taxon R) and is supported by eight un- and 137 (0 → 1), humerus bears intercon- equivocal synapomorphies: characters 70 (0 dylar ridge. If Perchoerus is excluded from → 1), embrasure pits on the palate present; Suina (®g. 9: taxon ``S''), then Suina has a 99 (1 → 2), strong parastyle on M1; 101 (0 branch support of three. In addition, seven → 1), M2 metacone half the size of the para- character states are optimized to have cone; 110 (0 → 2), paraconule absent evolved at this node, including characters 25 (O'Leary, 1998a); 115 (0 → 1), lower molar (1 → 0), contact between exoccipital and ec- paraconid or paracristid directly anterior to → → totympanic bulla absent; 57 (2 3), anterior protoconid; 116 (0 2), hypoconulid on M3 edge of orbit over M3;65(1→ 0), anterior absent (Thewissen, 1994; O'Leary, 1998a; opening of infraorbital canal between M1 and Geisler and Luo, 1998); 120 (0 → 1), lower P4,66(0→ 1), lateral surface of maxilla is molar protoconids approximately twice the highly concave; 95 (0 → 1), P4 metacone pre- height of molar hypoconids (Prothero et al., sent; 96 (1 → 0), P4 entocingulum absent; 1988); and 123 (0 → 1), talonid basins nar- and 176 (1 → 2), distal ends of metapodials row transversely with hypoconids centered have keels that wrap around onto their an- on the teeth (Thewissen, 1994; O'Leary, terior sides. 1998a; Geisler and Luo, 1998). The clade in- Camelidae, Ruminantia, and extinct rela- cluding Mesonychidae and Cetacea but ex- tives form several clades in all most parsi- cluding Hapalodectidae has a branch support monious trees to the exclusion of Hippopo- of two and is diagnosed by three unequivocal tamidae, Suidae, and Tayassuidae. Neoselen- synapomorphies: characters 7 (0 → 1), small odontia has a branch support of one (®gs. 8, postglenoid foramen; 45 (1 → 0), foramen 9: clade N) and is supported by six unequiv- ovale anterior to glenoid fossa (Geisler and ocal synapomorphies: characters 35 (0 → 1), Luo, 1998); and 111 (1 → 2), only one cusp anterior wall of facial nerve sulcus formed in the posterolingual quadrant of the upper by ectotympanic bulla; 133 (0 → 1), small molars. Unlike O'Leary (1998a), but similar supraspinatus fossa on the scapula; 154 (0 → to Geisler and Luo (1998) and Luo and Gin- 1), tibia and ®bula fused at proximal ends; gerich (1999), Hapalodectes is the sister 161 (1 → 0) lateral surface of proximal half group to a clade that includes Cetacea and of astragalus is concave; 172 (1 → 3), middle mesonychids. Luo and Gingerich (1999) list- portion of second metatarsal absent; and 174 ed several basicranial characters that unite (1 → 3), middle portion of ®fth metatarsal mesonychids and cetaceans. One of these, absent. Webb and Taylor (1980) listed the fu- enlargement of the tegmen tympani, is inter- sion of the ectocuneiform with the mesocu- preted here as an equivocal synapomorphy of neiform as a synapomorphy of Neoseleno- Acreodi because it cannot be scored in Ha- dontia. However, the fusion also occurs in palodectes. Their character 37, shape of the Merycoidodon and Agriochoerus, and it external auditory meatus, is split into two therefore supports a larger clade including characters: character 39, angle of the mastoid Neoselenodontia and Oreodontoidea. Within process of the petrosal, and character 40, Neoselenodontia is a clade that includes Ca- length of external auditory meatus. An elon- melidae, Ruminantia, Xiphodontoidea, gate external auditory meatus supports a Oromerycidae, and Cainotherium but ex- clade that includes derived mesonychids (i.e., cludes Protoceratidae. This clade has a Sinonyx, Pachyaena, Mesonyx) and ceta- branch support of three and is diagnosed by ceans but excludes Dissacus. A sharp angle four unequivocal synapomorphies, including for the mastoid process of the petrosal is an characters 23 (0 → 1), stylohyoid oriented equivocal synapomorphy of Acreodi. anteroventrally; 62 (0 → 1), presence of a Unlike several previous morphological fenestra at the junction of the lacrimal, max- studies (O'Leary, 1998a; Geisler and Luo, illa, and frontal; 103 (0 → 1) M3 and M2 1998; Luo and Gingerich, 1999), Mesony- subequal; and 140 (0 → 1 or 2), radius and chidae was not monophyletic in the most par- ulna partially or completely fused. simonious trees for this matrix. Instead, the Acreodi (Hapalodectidae ϩ Mesonychidae early mesonychid Dissacus was the sister 26 AMERICAN MUSEUM NOVITATES NO. 40 group to a clade including Cetacea plus all in the other it is the sister group to a clade other mesonychids. The clade of Cetacea and that includes Equus and Neoselenodontia. all mesonychids except Dissacus has a The inclusion of Equus within the artiodactyl branch support of one and is diagnosed by clade as the sister group to Neoselenodontia two unambiguous synapomorphies: charac- renders Artiodactyla paraphyletic; however, ters 40 (2 → 3), long external auditory me- Cetacea is excluded from the artiodactyl → atus on the squamosal, and 102 (0 1), M1 clade, as in the analysis including both extant metaconid absent or forms a slight lingual and extinct taxa. Suoidea is paraphyletic in swelling on the protoconid. both most parsimonious trees with Hippo- Cetacea (®g. 8: clade C) has a relatively potamidae as the sister group to all other ar- high branch support of seven and is diag- tiodactyls and Equus. nosed by 15 unequivocal synapomorphies: characters 4 (0 → 1), sulcus for proximal sta- TESTING OTHER PHYLOGENIES pedial artery absent (O'Leary and Geisler, 1999); 10 (0 → 1), posttemporal canal ab- As a whole and on a clade-by-clade basis, sent; 14 (1 → 2), fossa for tensor tympani the controversial molecule-based phylogeny muscle forms a circular pit with an anterior (e.g., Gatesy et al., 1999b) that places Ceta- groove; 19 (0 → 1), pachyosteosclerotic bul- cea within three artiodactyl clades is strongly la (Thewissen, 1994; Luo, 1998; Luo and contradicted by the morphological data pre- Gingerich, 1999; O'Leary and Geisler, sented by this study. The shortest morphol- 1999); 24 (0 → 1), bulla articulates with the ogy-based tree that has a monophyletic squamosal via a circular entoglenoid process Whippomorpha is 1642 steps, or 7 steps lon- (Luo and Gingerich, 1999; O'Leary and ger than the shortest trees (®g. 11: clade W). Geisler, 1999); 38 (0 → 1), mastoid process A monophyletic Cetruminantia occurs in of petrosal not exposed posteriorly (O'Leary trees 23 steps longer (®g. 11: clade CR), and and Geisler, 1999); 44 (1 → 0), preglenoid Artiofabula occurs in trees 18 steps longer process absent; 49 (1 → 0), alisphenoid canal (®g. 11: clade AF). The shortest morpholo- absent (O'Leary and Geisler, 1999); 93 (0 → gy-based tree that includes all of these clades 1), P4 protocone absent (O'Leary, 1998a; and is fully compatible with the most parsi- O'Leary and Geisler, 1999); 94 (0 → 1), P4 monious trees of Gatesy et al., (1999b) has paracone greater than twice the height of M1 1660 steps, or 25 steps longer than the length paracone (Thewissen, 1994; O'Leary, 1998a; of the unconstrained most parsimonious O'Leary and Geisler, 1999); 95 (1 → 0), P4 trees. The shortest tree that is also compatible metacone absent, 99 (2 → 0 or 1), M1 par- with the most parsimonious trees of O'Leary astyle weak or absent; 103 (2 → 1), M3 and and Geisler (1999) is 1674 steps (®g. 1A), M2 subequal; 114 (0 → 1), lingual cingulid much longer than the molecule-based topol- on lower molars present (O'Leary, 1998a; ogy. This result is not surprising because the O'Leary and Geisler, 1999); and 122 (1 → 2 constraint based on O'Leary and Geisler's to 0), reentrant groove on lower molars ab- (1999) study speci®es the position of 39 taxa, sent or on mesial side of tooth. while the molecule-based constraint only speci®es the position of 17.

EXTANT TAXA ONLY DISCUSSION If the matrix is analyzed with all extinct ARTIODACTYL MONOPHYLY taxa deleted, the result is two most parsimonious trees of 587 steps long (length in- As in the studies of Geisler and Luo cludes polymorphisms). Several groups are (1998) and O'Leary and Geisler (1999), Ar- common to both most parsimonious trees, in- tiodactyla was monophyletic in all shortest cluding Ruminantia, Camelidae, Neoseleno- trees, even though cetaceans are not scored dontia, Hippopotamidae, Cetacea, and Odon- for several postcranial characters that support toceti. The only difference between the two artiodactyl monophyly (®g. 8: taxon A). trees is the position of Tayassu. In one tree Forcing Cetacea, but not mesonychids, to a it is the sister group to Sus (®g. 10A), while topological position inside Artiodactyla re- 2001 GEISLER: ARTIODACTYLA, CETACEA, MESONYCHIDAE 27

Fig. 10. A. One of two most parsimonious trees based on the morphological data in appendix 3, if all extinct taxa and their character codings are excluded from the phylogenetic analysis. Sus and Tayassu do not form a clade in the other shortest tree; instead, Tayassu is the sister group to Neoselenodontia and Equus. Tree A has a length of 483 steps. B. The most parsimonious tree based on all data in appendix 3; unlike tree A, all taxa were included in the analysis (see ®g. 8). The extinct taxa were pruned from the tree in ®g. 8 to produce tree B, and the length was recalculated as 490 steps with all extinct taxa and their codings removed. C. The most parsimonious tree from the WHIPPO-2 matrix of Gatesy et al. (1999a); by using the data for extant taxa only in appendix 3, the tree length is 499 steps. Unlike O'Leary and Geisler (1999), if all extinct taxa are excluded, the most parsimonious trees still exclude Cetacea from the clade including all extant artiodactyls (tree A). Even though the topology of the most parsimonious tree for the morphology matrix does not have a monophyletic Artiodactyla (tree A), the hypothesis based on all taxa (tree B) is still more parsimonious than a molecule-based hypothesis (tree C) by 16 steps. Bold branches in trees denote the clade that includes all extant artiodactyls; taxa in bold are extant cetaceans. Cetacea is excluded from the artiodactyl clade in trees A and B, while it is included within the artiodactyl clade in tree C. quires that most of the dental and basicranial placing cetaceans and mesonychids as a similarities between mesonychids and ceta- clade outside of Artiodactyla leads to shorter ceans be reinterpreted as convergence. If morphology-based trees. Even though the both cetaceans and mesonychids are placed postcrania of the early cetacean Ambulocetus inside Artiodactyla, then several of the post- are only partially known, like mesonychids cranial characters that support artiodactyl it differs from all extant artiodactyls in the monophyly must have reversed. Either way, following characters: centrale bone in the 28 AMERICAN MUSEUM NOVITATES NO. 40

analyses with all taxa (®g. 10B) are considerably shorter than the molecule-based trees of Gatesy et al. (1999b) (®g. 10C). Lengths of trees were calculated using the morphological matrix scored for extant taxa only. The shortest tree based on morphology that is also consistent with the most parsimonious trees from the analysis with all taxa is 610 steps long, while the shortest tree based on morphology that is consistent with the molecule-based hypothesis of Gatesy et al. (1999a) is 16 steps longer, or 626 steps. Even though the topology of the most parsimonious trees and the recovery of artiodactyl monophyly is sensitive to taxon sampling, morphological data contradict the molecule- based phylogeny with and without extinct taxa.

BASAL ARTIODACTYLS Fig. 11. The molecule-based tree from Gatesy et al. (1999a) with the degree (number of steps) Whereas there is general agreement on the that the data in appendix 3 contradict phyloge- monophyly of families within Artiodactyla, netic hypotheses depicted in this tree. Clade the higher level phylogeny within Artiodac- names are placed immediately below and to the tyla is controversial, including which taxon left of their respective nodes, while branch sup- occupies the most basal branch. Diacodexis port values are placed above and to the left. Neg- has been suggested to be the most primitive ative values indicate that these groupings do not occur in the most parsimonious trees. Taxa abbre- artiodactyl by several authors (Matthew, viations: AF, Artiofabula; CR, Cetruminantia; W, 1934; Rose, 1985; Geisler and Luo, 1998; Whippomorpha. O'Leary and Geisler, 1999); however, both Rose (1982) and Gentry and Hooker (1988) hypothesized that Diacodexis is more closely related to selenodont artiodactyls based on wrist, an astragalar foramen, and a third tro- structures in the limbs that they interpreted chanter on the femur (Thewissen et al., as cursorial adaptations. The most parsimo- 1996). nious trees for the morphology matrix of this Unlike the morphology-based matrix of study support a basal position for both spe- O'Leary and Geisler (1999), the exclusion of cies of Diacodexis, with Wasatchian Diacod- Cetacea from Artiodactyla in all most parsi- exis being the sister group to a clade includ- monious trees derived in this study is not en- ing Diacodexis pakistanensis and all other tirely dependent on the inclusion of extinct artiodactyls (®gs. 8, 9). Placing both species taxa and their respective character codings in of Diacodexis as sister groups to the clade of the phylogenetic analyses. If all extinct taxa selenodont artiodactyls, which has Bunome- and their characters codings are deleted from ryx as its most basal member, increases tree the morphological data set of this study, a length by 9 to 10 steps. parsimony analysis produces trees that have Cetacea excluded from the clade that in- SUIFORM ARTIODACTYLS cludes living artiodactyls; however, Artio- dactyla is not monophyletic in these trees be- There has been little consensus concerning cause Equus forms the sister group to a ru- the relationships of extinct artiodactyls to minant and camel clade (®g. 10A). Even Hippopotamidae, Tayassuidae, and Suidae. though Artiodactyla is not monophyletic in In the analysis with some multistate charac- analyses with all data for extinct taxa ex- ters ordered by O'Leary and Geisler (1999: cluded, the most parsimonious trees from the ®g. 8), Elomeryx and then Archaeotherium 2001 GEISLER: ARTIODACTYLA, CETACEA, MESONYCHIDAE 29

(genus in artiodactyl family Entelodontidae) ic process is expanded ventrally; however, form successive sister groups to Sus. The the sutures between the tympanic and squa- placement of Entelodontidae as closer to Sui- mosal in available, juvenile specimens of na (Suidae ϩ Tayassuidae) than to Hippo- Perchoerus are fused, making it impossible potamidae is also a feature of the preferred to determine if the squamosal is expanded. and most parsimonious trees of Gentry and The teeth of Perchoerus resemble peccaries Hooker (1988). In the morphology-based in lacking many of the cusps of pigs; how- analyses of this study, Hippopotamidae and ever, the absence of these cusps is plesio- Suina (minus Perchoerus) form a clade to the morphic for Artiodactyla. The enlarged, hyp- exclusion of the extinct taxa Entelodontidae sodont upper and lower canines apparently and Elomeryx (®gs. 8, 9). This conclusion ally Perchoerus with Suoidea; however, it is mirrors Matthew's (1929, 1934) early ®nd- most parsimonious to place Perchoerus out- ings except for the more basal position of side of this group based on several primitive Perchoerus. A rede®ned Suiformes (see In- characters, including absence of cancellous troduction) is one of the more strongly sup- bone within the bulla, position of the fora- ported, higher level, morphology-based men ovale anterior to or in line with the an- clades within Artiodactyla, based on a branch terior edge of the glenoid fossa, and posterior support of three (®g. 8: taxon U), that con- edge of the foramen ovale formed by the ali- tradicts recent molecule-based phylogenies sphenoid. Trees that have a sister-group re- (e.g., Gatesy et al., 1999b). Almost all of the lationship between Perchoerus and Tayassu characters that support Suoidea have been are eight steps longer than the most parsi- scored in one or more basal cetaceans; there- monious trees. Entelodontidae plus extant fore, unlike characters of the hindlimb, these suoids form a clade to the exclusion of Per- characters will continue to support an artio- choerus in all most parsimonious trees. This dactyl clade to the exclusion of Cetacea, re- group is supported by three unequivocal syn- gardless of future fossil discoveries. apomorphies not found in Perchoerus: char- Unlike the phylogenetic hypotheses of acters 16 (0 → 1), absence of contact be- Gentry and Hooker (1988) and Colbert tween petrosal and basioccipital; 43 (1 → 0), (1935), the results of this study indicate that posterolateral border of glenoid fossa ¯at; anthracotheres (represented by Elomeryx) are and 103 (0 → 1), M2 and M3 subequal. not the sister group or potential ancestors to Hippopotamidae, but instead are the sister SELENODONT ARTIODACTYLS group to all other members of Suiformes (®gs. 2, 3). A basal position for anthracoth- Controversial aspects of the phylogeny of eres among suiform artiodactyls in this study selenodont artiodactyls include the af®nities corroborates similar views by Pickford of Protoceratidae, monophyly of Neoseleno- (1983). Placing Elomeryx as the sister group dontia, monophyly of Tylopoda (sensu Webb to the Hippopotamidae causes an increase in and Taylor, 1980), and the af®nities of Or- 9 or 11 steps, depending on the position of eodontoidea. The taxonomic history of Pro- this clade within Suiformes. toceratidae is very complex, with previous One surprising result of the phylogenetic workers advocating either ruminant or ca- analysis was a sister-group relationship be- melid af®nities (see Patton and Taylor, 1973). tween Perchoerus, which is considered a According to several studies, Protoceratidae basal peccary, and a clade that includes ex- and Camelidae, to the exclusion of rumi- tant members of Suina, Hippopotamidae, and nants, comprise the two major groups within Entelodontidae. Wright (1998: 391) listed the Tylopoda (Scott, 1940; Patton and Taylor, possession of a ``Platelike posttympanic pro- 1973; McKenna and Bell, 1997). By con- cess of squamosal having rounded lateral trast, the most parsimonious trees for the ma- edge'' as a synapomorphy of Tayassuidae in- trix of Gentry and Hooker (1988) included a cluding Perchoerus. It is unclear exactly sister group relationship between Ruminantia what this character refers to because this and Protoceratidae; however, they rejected structure is rounded in Sus and Tayassu. In this hypothesis for a less parsimonious one Tayassu and other peccaries, the posttympan- that grouped Cameloidea and Protoceratidae 30 AMERICAN MUSEUM NOVITATES NO. 40 together. This study provides another alter- otherium with Camelidae and Oromerycidae nativeÐthat Protoceratidae (®g. 9: taxon T) are characters 28 (2 → 1), short meatal tube is the sister group to a camel and ruminant of the ectotympanic; 31 (0 → 1), posterior clade. If Protoceratidae is placed as the sister edge of squamosal sharply upturned; 43 (1 group to Cameloidea (Camelidae ϩ Orom- → 0), posterolateral edge of glenoid fossa ¯at erycidae), then the minimal length is 10 steps and not notched; 45 (2 → 1), foramen ovale longer; if it is placed as the sister group to anterior to glenoid fossa or in line with its Cameloidea ϩ Cainotherium, then the mini- anterior edge; 57 (1 → 2), anterior edge of mal length is 6 steps longer. Most of the orbit over M2 or M2/M3 division; 63 (0 → 1), characters listed by Patton and Taylor (1973) anterior edge of jugal over M1 or M1/M2 di- linking protoceratids with camels are primi- vision; and 65 (2 → 1) facial infraorbital fo- tive for artiodactyls (Janis et al., 1998), as ramen over P3/P4 division. determined here by optimization on the most Webb and Taylor (1980) named Neoselen- parsimonious trees of this study and by com- odontia for the clade including tylopods and parison to Diacodexis. Examples include Ruminantia, and they listed characters to di- separation of the navicular and cuboid, mag- agnose it. The most parsimonious trees for num and trapezoid, and third and fourth the matrix of Gentry and Hooker (1988) in- metacarpals. clude a monophyletic Neoselenodontia; how- According to Webb and Taylor (1980), Ty- ever, they discarded this hypothesis in favor lopoda includes Camelidae, Oromerycidae, of one that has a polyphyletic Neoselenodon- Xiphodontidae, Amphimerycidae, and Pro- tia, with ruminants and camels evolving from toceratidae. As previously mentioned, this two different groups of extinct artiodactyls. data matrix contradicts a close relationship Stucky (1998) also favored a paraphyletic between Protoceratidae and Camelidae. In all Neoselenodontia with Homacodon and Bun- most parsimonious trees (®gs. 8, 9), Rumi- omeryx as basal members of a tylopod clade nantia and Camelidae form a clade to the ex- and the primitive artiodactyls Pentacemylus clusion of Xiphodontoidea; therefore, tylo- and Mesomeryx as the sister group(s) to pods form a paraphyletic group, with most Ruminantia. The phylogenetic analyses of tylopods being more distantly related to cam- the morphological matrix of this study sup- els than ruminants are. Even though most ty- port a monophyletic Neoselenodontia (®gs. lopods do not appear to be closely related to 8, 9: clade N); however, the support for this camels, Cameloidea (Camelidae and Orom- erycidae) occurs in all most parsimonious group is low, with branch support of one. trees and corroborates the work of previous Cameloidea, Cainotherium, and Ruminantia authors (Wortman, 1898; Scott, 1898, 1899, form a clade within Neoselenodontia to the 1940) (®g. 9: taxon CA). Cameloidea is sup- exclusion of Xiphodontoidea and Protocera- ported by the following synapomorphies in tidae in the strict consensus (®g. 8). The all most parsimonious trees: characters 64 (1 branch support for this clade is three, and it → 2), facial part of skull long; 65 (1 → 0), is supported by four unequivocal synapo- infraorbital canal over M1 or P4;79(1→ 0), morphies. Both Neoselenodontia and the clade excluding Xiphodontoidea and Proto- depth of dentary constant between M1 and → ceratidae contradict the molecule-based phy- M3;85(1 0), lower canine larger than incisors; and 125 (0 → 1), anteroventral border logeny of Gatesy et al. (1999a), which has of occipital condyle ¯ared laterally. Cainoth- Camelidae as the basal branch of Artiodac- erium is the sister group to Cameloidea in tyla and Ruminantia as the sister group to the strict consensus, which is considerably Whippomorpha. Like one of the analyses of different from the most parsimonious trees of O'Leary and Geisler (1999: ®g. 8), a sister- Gentry and Hooker (1988), who placed group relationship between Neoselenodontia Cainotheriidae as the sister group to a clade and Oreodontoidea was also found in all that includes all tylopods, Ruminantia, and most parsimonious trees. This position for Amphimerycidae. Based on this matrix, their Oreodontoidea contradicts Gentry and Hook- phylogeny requires an additional 13 steps. er's (1988) conclusion that oreodonts are bas- Characters that support the grouping of Cain- al tylopods. 2001 GEISLER: ARTIODACTYLA, CETACEA, MESONYCHIDAE 31

OTHER HYPOTHESES two anonymous reviewers. C. Tarker and L. Meeker instructed and advised me on the Not only are the molecule-based clades photographs in ®gures 2 through 7. Any mis- Whippomorpha, Cetruminantia, and Artiofa- takes in these images are my own. I would bula not in any of the most parsimonious like to acknowledge several individuals who trees of this study, they are strongly contra- generously provided access to specimens, dicted by the morphological data in appendix some of them undescribed: P. D. Gingerich, 3. Trees consistent with the molecule-based R. E. Heizmann, D. Lunde, Z. Luo, M. C. hypothesis of Gatesy et al. (1999a) are at McKenna, B. Randall, N. B. Simmons, and least 25 steps longer than the most parsi- J. G. M. Thewissen. During the development monious trees. A substantial amount of the of this paper I greatly bene®ted from discus- data presented in this study has not been pre- sions with Z. Luo, P. Makovicky, M. C. Mc- viously included in a cladistic analysis; Kenna, J. Meng, and D. Pol. I am very grate- therefore, these tests are novel. As with mo- ful to M. C. McKenna and D. Pol for use lecular data (Gatesy et al., 1999b), the addi- (and sometimes overuse) of their computers. tion of new morphological data corroborates D. Pol allowed me to use an unpublished previous morphology-based hypotheses and macro program for calculating branch sup- does not lead to novel phylogenetic hypoth- port and also patiently instructed me in the eses. The most parsimonious trees for appen- ways of NONA. This research was supported dix 3 include most of the clades found by by a National Science Foundation Graduate O'Leary and Geisler (1999: ®g. 8), such as Fellowship. Additional support came from Artiodactyla, Suiformes, Neoselenodontia, the Of®ce of Grants and Fellowships and the and a clade including Mesonychidae ϩ Ha- Department of Vertebrate Paleontology at the palodectidae ϩ Cetacea. American Museum of Natural History. Despite the rejection of molecule-based hypotheses by this study, the strict consensus in ®gure 8 should not be taken as the best, REFERENCES overall hypothesis for artiodactyl and ceta- Barnes, L. G. cean phylogeny. Both molecular and mor- 1984. Whales, dolphins and porpoises: origin phological data can test phylogenetic hypoth- and evolution of the Cetacea. In T. W. eses as well as be explained by them; there- Broadhead (ed.), Mammals. Notes for fore, the best hypothesis should be based on a short course organized by P. D. Gin- a combined analysis of both types of data gerich and C. E. Badgley. Univ. Ten- (Nixon and Carpenter, 1996). A project in nessee Dep. Geol. Sci. Stud. Geol. 8(1± 4): 139±154. progress aims to do just that (Geisler, in Bremer, K. prep.); however, a caveat of such ``total ev- 1988. The limits of amino acid sequence data idence'' projects is that characters interpreted in angiosperm phylogenetic reconstruc- as homoplasy remain unexplained. Until an tion. Evolution 42: 785±803. alternative explanation is presented, the phy- 1994. Branch support and tree stability. Cla- logeny in ®gure 8 is the best explanation for distics 10: 295±304. morphological data and potentially falsi®es Carpenter, J. M. the molecule-based hypotheses. The chal- 1996. Uninformative bootstrapping. Cladis- lenge for future studies is to develop hypoth- tics 12: 177±181. eses that simultaneously explain con¯icting Cifelli, R. L. 1982. The petrosal structure of Hyopsodus types of data. Such attempts will certainly with respect to that of some other un- require us to go beyond the boundaries of a gulates, and its phylogenetic implica- most parsimonious cladogram for a scienti®c tions. J. Paleontol. 56: 795±805. explanation. Coddington, J., and N. Scharff 1994. Problems with zero-length branches. ACKNOWLEDGMENTS Cladistics 10: 415±423. Colbert, E. H. The quality of the manuscript was greatly 1935. Distributional and phylogenetic studies improved by the careful reviews of M. C. on Indian fossil mammals. IV. The phy- McKenna, N. B. Simmons, M. D. Uhen, and logeny of the Indian Suidae and the or- 32 AMERICAN MUSEUM NOVITATES NO. 40

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APPENDIX 1

SPECIMENS AND REFERENCES ARCHAIC UNGULATES Two of the OTUs were families, and the allocation of genera to Leptictidae and Entelodontidae Arctocyon: AMNH-VP 55900 (cast), 55901 follows McKenna and Bell (1997). (cast), 55902; Russell (1964). Eoconodon: AMNH-VP 764, 774, 3177, 3181, OUTGROUPS 3187, 3280, 4052, 16329, 16341; Matthew (1897, 1937). Ictops: AMNH-VP 38920, 76745. Hyopsodus: AMNH-VP 1, 39, 1717, 10977, Leptictis: AMNH-VP 1413a, 5346, 38920, 10979, 11330, 11349, 11350, 11363, 11393, 39444, 90256, 96766; MCZ 19678; USNM 11415, 11899; Gazin (1968); Thewissen and 336367; Matthew (1918); Novacek (1980, 1986). Domning (1992). Orycteropus afer: AMNH-VP 2285. Meniscotherium: AMNH-VP 2560, 4412, 4413, 4414, 4426, 4434, 4447, 48083, 48120, 48121, OTHER NONUNGULATE MAMMALS 48122, 48125, 48126, 48127, 48129, 48555; Ga- Vulpavus: AMNH-VP 1900, 19198, 11497, zin (1965); Cifelli (1982); Williamson and Lucas 12626; Heinrich and Rose (1997). (1992). Canis: AMNH-VP 2288, 2853, 3043; Evans Phenacodus: AMNH-VP 293, 2961 (cast), (1993). 4370, 4378, 4403, 15262, 15266, 15268, 15271, Rattus norvegicus: AMNH-VP 180, 181, 2925; 15275, 15279, 15286, 16791, 16794, 117195 Greene (1935). (cast); Thewissen (1990). 2001 GEISLER: ARTIODACTYLA, CETACEA, MESONYCHIDAE 39

CETACEA ARTIODACTYLA

Ambulocetus natans: HGSP 18507; Thewissen Agriochoerus: AMNH-VP 685, 1349, 1178, et al. (1996). 1355, 1490, 7402, 7406, 7407, 7409, 7410, 7420, Balaenoptera: AMNH-M 28274, 84870, 9808, 9811, 38843, 38932, 95324, 95332, 99275. 148407, 219212, 219220; Daudt (1898); MuÈller Amphimeryx: Stehlin (1910); Pearson (1927); (1898); Sokolov (1982). Dechaseaux (1974). Basilosaurus: AMNH-VP 141381, 61990, Archaeotherium: AMNH-VP 569, 1277, 1278, 129577; GSP-UM 97507 (cast); Kellogg (1936). 1483, 2176, 6389, 7380, 11323, 12461, 26176, Delphinapterus leucas: AMNH-M 34868, 39010, 39018, 39127, 39455, 53602, 53609, 34937, 34944, 77789, 185300. 82454, 90101, 102091, 18±537. Georgiacetus vogtlensis: GSM 350; Hulbert et Bos taurus: AMNH-M 147192, 147193, al. (1998); Hulbert (1998). 147194, 180379, 212982, 212986, 212987; Sisson Pakicetus: GSP-UM 084 (cast), HGSP 96231, (1921); Dyce et al. (1987). 96386, 96431; Gingerich and Russell (1981, Bunomeryx montanus: AMNH-VP 2066, 2070, 1990); Thewissen and Hussain (1993); Thewissen 2071; Norris (1999). (1994); Luo (1998). Cainotherium: AMNH-VP 10277, 55333, Physeter catodon: AMNH-M 80206, 34872; 55337; HuÈrzeler (1936). Omura et al. (1962). Camelus: AMNH-M 2911, 14109, 35379, Protocetus atavus: SMNS 11084, Fraas (1904). 35463, 35563, 63850, 69405, 80227, 90433; Remingtonocetus harudiensis: GSP-UM 3009, Smuts and Bezuidenhout (1987). 3054, 3057; Kumar and Sahni (1986); Gingerich Cebochoerus: AMNH-VP 111093, 11094, et al. (1995). 11095, 105081, 105458; Pearson (1927); Decha- Tursiops truncatus: AMNH-M 120920, seaux (1974). 184930, 212554; Slijper (1966); Fanning and Har- rison (1974). Diacodexis pakistanensis: Russell et al. (1983); Thewissen et al. (1983); Thewissen and Hussain (1990). MESONYCHIDAE Wasatchian Diacodexis (probably D. metsiacus): AMNH-VP 4700, 16141, 128563 (cast); Dissacus navajovius: AMNH-VP 3356, 3359, Rose (1985). 3360, 3361, 15996. Elomeryx armatus: AMNH-VP 572, 579, 582, Dissacus praenuntius: AMNH-VP 16069, 1242, 1243, 1245, 1249, 1259, 1263, 1483, 131919 (cast); O'Leary and Rose (1995a); Luo 39015, 10041, 12461, SD 582, SD 23±491, 511, and Gingerich (1999). 101668; Scott (1894). Mongolian Dissacus: MAE-BU97±13786. Harpagolestes: AMNH-VP 1692, 1878, 1892, Entelodon: AMNH-VP 7380. 1945, 2302, 2308, 26267, 26300, 26301; Wort- Eotylopus reedi: AMNH-VP 53.4 (cast), 784, man (1901); Zhou et al. (1995). 47394, 47404, 88301; Scott (1940). Mesonyx obtusidens: AMNH-VP 11552, Gobiohyus orientalis: AMNH-VP 26277, 12643, 93451; Scott (1888). 26274, 26282. Pachyaena gigantea: AMNH-VP 72, 2959, Heteromeryx dispar: AMNH-VP 12326. 15226, 15227; O'Leary and Rose (1995b); Rose Hexaprotodon liberiensis: AMNH-M 2423, and O'Leary (1995). 52465, 81899, 89626, 146848, 146849, 148452, Pachyaena ossifraga: AMNH-VP 75, 4262, 185383, 202423, 214182; Sokolov (1982). 4263, 15222, 15224, 15730, 16154; O'Leary and Hippopotamus amphibius: AMNH-M 130247, Rose (1995b). 15898, 176118, 24282, 24284, 24287, 24285, Sinonyx jiashanensis: IVPP V10760; Zhou et 24289, 53773, 54248, 54249, 80183, 80813, al. (1995). 81856, 99637, 130247, 70019; Langer (1988); So- Synoplotherium canius: AMNH-VP 19203; kolov (1982). Wortman (1901). Homacodon vagans: AMNH-VP 12695, 12138, 12139; Marsh (1894). Hypertragulus: AMNH-VP 53802, 1341, HAPALODECTIDAE 53804, 7918, 53801, 53803, 7944, 7933, Lusk-0- Hapalodectes hetangensis: IVPP V5253; Ting 146-4024, (H) 326±654. and Li (1987). Lama: AMNH-M 14121, 146543, 70424, 6291, Hapalodectes leptognathus: AMNH-VP 78, 6235, 40842, 100276, 247748, 46, 40846, 12781, 128561, 14748 (cast); Szalay (1969); 147879, 80113. O'Leary (1998b). Leptomeryx: AMNH-VP 53710, 53721, 11870, 40 AMERICAN MUSEUM NOVITATES NO. 40

38910, 53663, 39123, 53711, 6616, 39450, Sus scrofa: AMNH-M 45, 5450, 20871, 54508, 53571, (S) 606±25834, 542±24617, 611±26621. 69422, 100260, 135020, 235190, 235192, Leptoreodon marshi: AMNH-VP 2064. 236144, 236145, 238325, 238331, 694422; So- Merycoidodon: AMNH-VP 1287, 39425, kolov (1982). 45250; FAM 49690, 72205, 72238, 72258, Tayassu tajacu: AMNH-M 66748, 25978, 45217A, 45217B, 72186B, 49644, 72286; AM 28954, 28955, 36703, 29446, 29442, 141992, 595, 1297, 610, 9793, 594. 215154, 17352. Mixtotherium: AMNH-VP 10443, 10445, Tragulus: AMNH-M 548, 32645, 37210, 100019, 107617, 105080; Stehlin (1908); Pearson 53602, 53609, 60759, 90101, 90193, 10101, (1927); Dechaseaux (1974). 102091, 102176, 103700, 14137, 14139, 34252, Odocoileus virginianus: AMNH-M 152, 7377, 106552, 188310, 240913, 244375. 24410, 37617, 20797, 244603, 238469, 238644, 245629, 238469. Xiphodon: Cuvier (1822); Stehlin (1910); De- Ovis: AMNH-M 875, 6231, 6239, 35520, chaseaux (1967). 88702, 10074, 10261, 14515, 15584, 35316, 35816, 35851, 70084, 80120, 100072, 119634, PERISSODACTYLA 146547, 53589; Sokolov (1982). Perchoerus: AMNH-VP 585, 695, 1200, 1282, Equus caballus: AMNH-VP 272, 273, FM 99, 1285, 7391, 7392, 7394, 7395, 7398, 9794, 9813. FM 129; Sisson (1921); Langer (1988). Poebrotherium: AMNH-VP 6515, 8955, 9352, 9804, 13034, 38990, 39085, 39446, 41317, Mesohippus: AMNH-VP 673, 74001, 74019, 42240, 42248, 42249, 42261, 42272, 42276, 74025, 74048, 74063, 111744, 116325, 116344, 42277, 42281, 42284, 42290, 42292, 47003, 116345, 116374. 47008, 47016, 47022, 47027, 47052, 47093, Heptodon: AMNH-VP 294, 485, 4858, 14884, 47103, 47182, 47284, 47317, 47324, 47333, 16861, 141881, 14864, 14865, 16861; Radinsky 47707A, 47707B, 47907, 63704, 63712, 63713, (1965). 63756, 63757, 63761, 97103. Hyracotherium: AMNH-VP 118, 55267, Protoceras celer: AMNH-VP 1228, 584, 1222, 55268, 55269, 70197, 96274, 96277, 96283, 1223, 1224, 1220, 1229, 53521, 1226, 53527, 96298, 96734, 129209; Thewissen and Domning 1227, 644, 40878, 40879, 597, 643. (1992).

APPENDIX 2 MORPHOLOGICAL CHARACTERS posterior groove on promontorium, medial to the fenestrae rotundum and ovalis This appendix de®nes the 176 morphological (0); absent (1) (Cifelli, 1982; Thewissen characters used for cladistic analyses. Unquali®ed and Domning, 1992). citations indicate that the character is worded with 3. Internal carotid foramen.ÐAbsent or little or no modi®cation from the given reference. con¯uent with piriform fenestra (0); pre- Characters that are ``modi®ed'' from references sent at basisphenoid/basioccipital suture have been signi®cantly changed, and those that with lateral wall of foramen formed by are ``derived'' have been extracted from a diag- both these bones and thus separated from nosis or morphological description and converted the piriform fenestra (1) (Geisler and into a form ready for cladistic analysis. Multiple Luo, 1998). citations indicate more detailed descriptions, ad- 4. Sulcus on promontorium for proximal sta- ditional character states, illustrations, or other im- pedial artery.ÐPresent, forms a groove provements of a character, as compared to its ®rst that branches from the transpromontorial use. sulcus anteromedial to the fenestra rotundum and extends to the medial edge of VASCULAR the fenestra ovalis (0); absent (1) (Cifelli, 1982; Thewissen and Domning, 1992). 1. Medial edge of ectotympanic bulla.ÐNot 5. Foramen for ramus superior of stapedial notched (0); has notch and sulcus for the artery.ÐPresent (0); absent (1) (modi®ed internal carotid artery (1) (modi®ed from from Novacek, 1986; Thewissen and Webb and Taylor, 1980). Domning, 1992). 2. Transpromontorial sulcus for the internal 6. Position of foramen for ramus superior of carotid artery.ÐPresent, forms antero- stapedial artery.ÐLateral to epitympanic 2001 GEISLER: ARTIODACTYLA, CETACEA, MESONYCHIDAE 41

recess (0); anterolateral to epitympanic re- totympanic contacts tympanohyoid later- cess, adjacent to ventrally convex portion ally and petrosal medially, in some cases of the tegmen tympani (1). Cannot be ectotympanic separated from petrosal by scored for taxa that lack this foramen a narrow ®ssure (0); complete, ectotym- (modi®ed from Geisler and Luo, 1998; panic contacts both the tympanohyoid and O'Leary and Geisler, 1999). the petrosal (1) (modi®ed from Geisler 7. Size of postglenoid foramen.ÐLarge, and Luo, 1998; O'Leary and Geisler, much larger than fenestra ovalis of petro- 1999; Luo and Gingerich, 1999). sal (0); small, slightly larger than or equal 16. Articulation of pars cochlearis with ba- in size to the fenestra ovalis; absent (1) sisphenoid/basioccipital.ÐPresent (0); (modi®ed from Geisler and Luo, 1998; absent (1) (Thewissen and Domning, O'Leary and Geisler, 1999) 1992). 8. Position of postglenoid foramen (or- 17. Ectotympanic.ÐSimple ring (0); medial dered).ÐEnclosed entirely by the squa- edge expanded into bulla (1). Cannot be mosal (0); situated on petrosal/squamosal scored for taxa in which the ectotympanic suture, and if bulla present, a secondary is not preserved (derived from Novacek, ventral opening between the bulla and the 1977; MacPhee, 1981). squamosal may form (1) (modi®ed from 18. Ectotympanic bulla.ÐThin-walled, con- Geisler and Luo, 1998; O'Leary and tains middle ear space only (0); houses Geisler, 1999). middle ear space and highly cancellous 9. Mastoid foramen.ÐPresent, skull in pos- bone (1) (Gentry and Hooker, 1988). terior view (0); absent (1) (see MacPhee, 19. Pachyosteosclerotic involucrum of bul- 1994). la.ÐAbsent (0); present (1) (Thewissen, 10. Posttemporal canal (for arteria diploetica 1994; Luo, 1998). magna, also called percranial fora- 20. Lateral furrow of tympanic bulla.ÐAb- men).ÐPresent, occurs at petrosal/squa- sent (0); present, forms a groove on the mosal suture with skull in posterior view, lateral surface of the ectotympanic bulla the canal continues within the petrosal/ anterior to the base of the sigmoid process squamosal suture (0); absent (1) (Wible, (1) (Geisler and Luo, 1998; Luo and Gin- 1990; MacPhee, 1994). gerich, 1999). 21. Ventral in¯ation of ectotympanic bulla OTIC REGION AND SURROUNDING FEATURES (ordered).ÐAbsent, ventral edge of bulla dorsal to ventral edge of occipital con- 11. Subarcuate fossa.ÐPresent (0); absent (1) dyles (0); intermediate, edge of bulla at (Novacek, 1986). same level as occipital condyles (1); pre- 12. Shape of tegmen tympani (ordered).ÐUn- sent, ventral edge of bulla ventral to oc- in¯ated, forms lamina lateral to facial cipital condyles (2). nerve canal (0); in¯ated, forms barrel- 22. Posterior extension of bulla.ÐAbsent, shaped ossi®cation lateral to the facial stylohyoid does not rest in notch on pos- nerve canal (1); hyperin¯ated, transverse terior edge of bulla (0); present, bulla ex- width of tegmen tympani greater than or panded around stylohyoid forming notch equal to width of promontorium (2) (mod- on posterior edge of bulla (1); bulla ex- i®ed from Cifelli, 1982; Geisler and Luo, tends posterior to stylohyoid medially (2); 1998; Luo and Gingerich, 1999; O'Leary bulla extends posterior to stylohyoid lat- and Geisler, 1999). erally (3); dorsal end of stylohyoid com- 13. Anterior process of petrosal.ÐAbsent pletely enveloped or nearly so by bulla (0); present, anterior edge of tegmen tym- (4) (modi®ed from Gentry and Hooker, pani far anterior to edge of promontorium 1988). (1) (Geisler and Luo, 1998; Luo and Gin- 23. Orientation of stylohyoid.ÐVentral or gerich, 1999). ventrolateral, may rest in notch on the 14. Fossa for tensor tympani muscle.ÐShal- posterior edge of a tympanic bulla (0); low anteroposteriorly elongate fossa (0); anteroventral, may rest in longitudinal circular pit, no groove (1); circular pit furrow on ventral surface of a tympanic with deep tubular anterior groove (2); bulla (1). long narrow groove between tegmen tym- 24. Articulation of ectotympanic bulla to pani and promontorium (3) (Geisler and squamosal (ordered).ÐBroad articulation Luo, 1998; Luo and Gingerich, 1999). with medial base of postglenoid process 15. Stylomastoid foramen.ÐIncomplete, ec- (0); circular facet on elevated stage (1); 42 AMERICAN MUSEUM NOVITATES NO. 40

contact reduced to the falcate process of Ͻ15% of braincase height (1); substantial, the squamosal (2); contact absent (3) 20%Ͻ sagittal crest thickness Ͻ33% of (Geisler and Luo, 1998; Luo and Ginger- braincase height (2); dorsally expanded, ich, 1999). 39%Ͻ sagittal crest thickness Ͻ52% of 25. Contact between exoccipital and ectotym- braincase height (3). panic bulla.ÐAbsent (0), present (1) 34. Dorsal edge of braincase, relative to oc- (Geisler and Luo, 1998; Luo and Ginger- clusal plane.ÐSlopes posterodorsally (0); ich, 1999). approximately level relative to upper 26. Sigmoid process (homologous to anterior toothrow (1); curves posteroventrally (2). crus of tympanic ring).ÐAbsent (0); pre- 35. Facial nerve sulcus distal to stylomastoid sent, forms transverse plate that projects foramen.ÐAbsent (0); anterior wall of dorsolaterally from the anterior crus of sulcus formed by squamosal (1); anterior the ectotympanic ring and forms the an- wall formed by mastoid process of petro- terior wall of the external auditory meatus sal (2); anterior wall formed by meatal (1) (modi®ed from Thewissen, 1994; tube of ectotympanic (3) (modi®ed from Geisler and Luo, 1998; Luo and Ginger- Geisler and Luo, 1998; O'Leary and ich, 1999). Geisler, 1999). 27. Morphology of sigmoid process.ÐThin 36. Length of mastoid process of petrosal (or- and transverse plate (0); broad and ¯aring, dered).ÐVentral portion absent (0); ven- base of the sigmoid process forms dor- tral portion short, Ͻ70% of the antero- soventral ridge on lateral surface of ec- posterior length of promontorium (1); totympanic bulla (1) (Geisler and Luo, elongate, Ͼ100% length of promontorium 1998; Luo and Gingerich, 1999). (2); hypertrophied, Ͼ200% length of pro- 28. Ectotympanic part of the meatal tube (or- montorium (3) (modi®ed from Geisler dered).ÐAbsent (0); present but short, and Luo, 1996; Luo and Marsh, 1996; length of tube Ͻ30% the maximum width Geisler and Luo, 1998). of the bulla (1); present and long, length 37. Lateral exposure of mastoid process of Ͼ60% maximum width of bulla (2) (Geis- petrosal (ordered).ÐPresent between ex- ler and Luo, 1998). occipital and squamosal (0); constricted, 29. Basioccipital crests (falcate processes).Ð dorsal part of exposure forms lamina (1); Absent (0); present, form ventrolaterally absent (2) (modi®ed from Geisler and ¯aring basioccipital processes (1) (de- Luo, 1996; Luo and Marsh, 1996). rived from Barnes, 1984; modi®ed from 38. Mastoid process of petrosal.ÐExposed Thewissen, 1994; Geisler and Luo, 1998). externally on posterior face of braincase as a triangle between the lambdoidal crest GLENOID,POSTGLENOID, AND TEMPORAL of the squamosal dorsolaterally, the ex- REGIONS occipital ventrally, and the supraoccipital medially (0); not exposed posteriorly, 30. Paroccipital process (ordered).ÐShort, in lambdoidal crest of squamosal in contin- posterior view distal end terminates dorsal uous contact with exoccipital and supra- to ventral edge of occipital condyle (0); occipital (1). intermediate size, extends just ventral to 39. Angle of suture of squamosal with petro- ventral edge of condyle (1); elongate, ter- sal or exoccipital, skull in ventral view minates far ventral to occipital condyle (ordered).ÐVery large, forms a 147Њ an- (2). gle with the sagittal plane (0); large, 31. Posterior edge of squamosal.ÐFlat (0); forms an angle between 127Њ and 125Њ sharply upturned (1); sharply upturned (1); angle between 111Њ and 105Њ (2), an- and bears dorsally projecting process (2) gle Ͻ100Њ (3). (modi®ed from Gentry and Hooker, 40. Length of external auditory meatus of the 1988). squamosal (ordered).ÐVery short or ab- 32. Lambdoidal crest.ÐPresent (0); absent or sent, length Ͻ4% of half the basicranial forms low ridge (1). width (0); short, length between 19% and 33. Sagittal crest (ordered).ÐAbsent or bare- 23% (1); intermediate length between ly present, dorsoventral thickness of crest 29% and 36% (2); long, length between Ͻ7% of dorsoventral height of braincase 41% and 45% (3); very long, length (measured from ventral edges of condyles Ͼ52%. to dorsalmost point of supraoccipital) (0); 41. Postglenoid process.ÐForms transversely small, 10%Ͻ sagittal crest thickness oriented and ventrally projecting ridge 2001 GEISLER: ARTIODACTYLA, CETACEA, MESONYCHIDAE 43

(0); ventrally projecting prong, roughly unbranched (1); present, branched (2) oval in coronal section (1). (Janis and Scott, 1987; Scott and Janis, 42. Glenoid fossa.ÐConcave longitudinally 1993). (0); ¯at longitudinally (1); convex longi- 54. Supraorbital process.ÐAbsent, region tudinally (2). over orbit does not project lateral from 43. Posterolateral border of glenoid fossa.Ð sagittal plane (0); present, laterally elon- Slightly downturned ventrally or ¯at (0); gate and tabular (1) (derived from Barnes, conspicuously notched with concave sur- 1984; Geisler and Luo, 1998). face facing posteroventrally (1). 55. Postorbital process of jugal (ordered).Ð 44. Preglenoid process.ÐAbsent (0); present, Absent (0); present but does contact fron- forms transverse, ventrally projecting tal (1); present and contacts postorbital ridge at anterior edge of glenoid fossa (1) process of frontal forming postorbital bar (modi®ed from Thewissen, 1994; Geisler (2) (modi®ed from Gentry and Hooker, and Luo, 1998). 1988). 45. Foramen ovale.ÐAnterior to glenoid fos- 56. Ventral edge of orbit.ÐProjects dorsally sa (0); medial to glenoid fossa (1) (de- (0); ¯ared laterally (1). rived from Zhou et al., 1995; Geisler and 57. Position of orbit relative to toothrow (or- Luo, 1998). dered).ÐOver P4 or P4/M1 division (0); 46. Posterior edge of foramen ovale.Ð over M1 or M1/M2 division (1); over M2 Formed by the alisphenoid (0); formed by or M2/M3 division (2); over or posterior the petrosal and or tympanic bulla (1); to M3 (3). formed by squamosal (2). 58. Lacrimal tubercle.ÐAbsent (0); present, 47. Dorsoventral thickness of zygomatic pro- situated on anterior edge of orbit adjacent cess of the squamosal (ordered).ÐSmall, to the lacrimal foramen (1) (Novacek, 7%Ͻ dorsoventral thickness of zygomatic 1986). process Ͻ15% of dorsoventral height of 59. Lacrimal foramina (ordered).ÐTwo (0); braincase (measured from ventral edges one (1); highly reduced (2); absent (3) of condyles to dorsalmost point of supra- (modi®ed from Gentry and Hooker, occipital) (0); intermediate, 17%Ͻ dor- 1988). soventral thickness of zygomatic process 60. Facial portion of lacrimal relative to the Ͻ28% of dorsoventral height of braincase orbit (ordered).ÐRestricted to orbital rim, (1); dorsoventrally deep, 32%Ͻ dorsoven- 15%Ͻ maximum anteroposterior length tral thickness of zygomatic process Ͻ40% of facial portion of lacrimal Ͻ30% of the of dorsoventral height of braincase (2). maximum anteroposterior diameter of the 48. Zygomatic portion of jugal.ÐDirected orbit (0); small facial portion present, posterolaterally (0); directed posteriorly 30%Ͻ length of facial portion of lacrimal (1). Ͻ67% of the orbital diameter (1); moderate facial portion present, 70%Ͻ length ORBITAL MOSAIC AND FORAMINA of facial portion of lacrimal Ͻ93% of the orbital diameter (2); large facial portion 49. Alisphenoid canal (alar canal).ÐPresent present, 100%Ͻ length of facial portion (0); absent (1) (Novacek, 1986; Thewis- of lacrimal Ͻ180% of the orbital diameter sen and Domning, 1992). (3). 50. Foramen rotundum.ÐAbsent, maxillary 61. Antorbital pit in lacrimal.ÐAbsent (0); division of trigeminal nerve exits skull present (1) (Janis and Scott, 1987; Scott through the sphenorbital ®ssure (0); present (1) (Novacek, 1986; Thewissen and and Janis, 1993). Domning, 1992). 62. Fenestra in rostrum at junction of lacri- 51. Contact of frontal and alisphenoid.ÐPre- mal, nasal, and maxilla.ÐAbsent (0); sent (0); absent, separated by orbitosphe- present (1) (Scott and Janis, 1993). noid (1) (Prothero, 1993). 63. Position of anterior edge of jugal (or- 4 52. Contact of frontal and maxilla in orbit.Ð dered).ÐAnterior to or over P (0); over 1 1 2 2 2 Absent (0); present (1) (Novacek, 1986; M or M /M division (1); over M or M / 3 3 Thewissen and Domning, 1992). M division (2); over or posterior to M (3). ORBITAL POSITION AND SURROUNDING FEATURES FACE AND PALATE

53. Supraorbital horns.ÐAbsent (0); present, 64. Elongation of face (ordered).ÐAbsent 44 AMERICAN MUSEUM NOVITATES NO. 40

and face short, face (de®ned as part of (modi®ed from Thewissen, 1994; Geisler skull anterior to anterior edge of orbit) and Luo, 1998). Ͻ85% of the remaining posterior part of 75. Elongation of coronoid process (or- the skull (de®ned as part between anterior dered).ÐAbsent, 50%Ͻ dorsal height of edge of orbit and posterior edge of occip- coronoid process Ͻ90% of the width of ital condyle) (0); long, 90% Ͻ face Ͻ the coronoid process (measurement taken 170% remaining part of skull (1); elon- at posterior base of coronoid process, im- gate, 190% Ͻ face Ͻ 230% remaining mediately anterior to mandibular condyle) part of skull (2). (1); moderate, 110%Ͻ dorsal height 65. Anterior opening of infraorbital canal Ͻ180% of its width (2); substantial, (ordered).ÐOver M1 or P4 (0); at level be- 200%Ͻ dorsal height Ͻ270% of its width tween P3 and P4 (1); anterior or over P3 (3). (2). 76. Height of coronoid process (ordered).Ð 66. Lateral surface of maxilla.ÐFlat or Low, 150%Ͻ height of coronoid (mea- slightly concave (0); highly concave (1). sured from ventral edge of mandible to 67. Posterior edge of nasals.ÐTerminate an- dorsal edge of coronoid) Ͻ190% of the

terior to orbit (0); extended posteriorly, depth of the mandible at M3 (0); high, terminate posterior to the anterior edge of 210%Ͻ height of coronoid Ͻ310% of the

the orbit (1). depth of the mandible at M3 (1); very 68. Palatine ®ssures (ordered).ÐEnlarged, high, 320%Ͻ height of coronoid Ͻ440%

transverse distance between lateral edges of the depth of the mandible at M3 (2). of palatine ®ssures Ͼ53% of the width of 77. Deep concavity on lateral surface of man- the palate in the same transverse plane dible between condyle and coronoid pro- (0); small, transverse distance between cess of dentary.ÐAbsent (0); present (1) lateral edges of palatine ®ssures Ͻ48% of (modi®ed from Gentry and Hooker, the width of the palate in the same trans- 1988). verse plane (1); absent (2). 78. Height of dentary condyle (ordered).Ð 69. Palate.ÐFlat (0); vaulted, portion along Low, 60%Ͻ height of condyle (measured sagittal plane well dorsal to lateral edge from ventral edge of mandible to dorsal (1). edge of condyle but excluding any portion 70. Embrasure pits on palate.ÐAbsent (0); of the mandible that extends ventrally be-

present, situated medial to the toothrow, low the edge of the mandible at M3) accommodate the cusps of the lower den- Ͻ140% of the depth of the mandible at

tition when the mouth is closed (1) (mod- M3 (0); moderately elevated, 160%Ͻ i®ed from Thewissen, 1994; Geisler and height of condyle Ͻ230% of the depth of Luo, 1998). the mandible (1); well elevated, 240%Ͻ 71. Posterior margin of external nares (or- height of condyle Ͻ300% of the depth of dered).ÐAnterior to or over the canines the mandible (2). (0); between P1 and P2 (1); posterior to P2 79. Ramus of mandible.ÐApproximately

(2) (Geisler and Luo, 1998). same dorsoventral thickness from M1 to M3 (0); deepens posteriorly from M1 to MANDIBULAR M3 (1) (modi®ed from Gentry and Hook- er, 1988). 72. Angular process of mandible.ÐNo dorsal 80. Mandibular symphysis.ÐUnfused (0); hook (0); dorsal hook present (1) (Gentry fused (1) (Pickford, 1983). and Hooker, 1988). 73. Angle of mandible.ÐDistal end at same INCISORS AND CANINES level as ventral edge of dentary below molars (0); forms distinct ¯ange that pro- 81. I1 and I2.ÐPresent (0); absent (1). jects posteroventrally well below ventral 82. Rostrum.ÐPremaxillae short with inci- edge of dentary below molars (1) (modi- sors arranged in transverse arc (0); pre- ®ed from Gentry and Hooker, 1988). maxillae elongate, incisors aligned longi- 74. Mandibular foramen (ordered).ÐSmall, tudinally with intervening diastemata (1) maximum height of opening 25% or less (modi®ed from Prothero et al., 1988;

the height of the mandible at M3 (0); en- Thewissen, 1994). larged and continuous with a large pos- 83. Lower incisors.ÐApex of cusp pointed or terior fossa, maximum height greater than narrower than base (0); spatulate, apex of

50% the height of the mandible at M3 (1) cusp wider than base (1); peg-shaped, 2001 GEISLER: ARTIODACTYLA, CETACEA, MESONYCHIDAE 45

width of base equal to width of tip of weak (1); moderate to strong (2) (Zhou et tooth (2); tusklike (3). al., 1995; O'Leary, 1998a).

84. Elongation and transverse compression of 100. M1 metaconid.ÐPresent (0); absent (1) upper canines.ÐAbsent (0); present (1). (Thewissen, 1994). If sexually dimorphic, score for males 101. M2 metacone (ordered).ÐDistinct cusp, only (modi®ed from Webb and Taylor, subequal to paracone (0); distinct cusp, 1980). approximately half the size of the para- 85. Lower canine size.ÐLarger than incisors cone (1); highly reduced, indistinct from (0); approximately same size as incisors paracone (2) (Zhou et al., 1995; O'Leary, (1). 1998a).

86. Lower canine shape.ÐOval in cross sec- 102. M2 metaconid.ÐPresent, forms distinct tion (0); triangular or D-shaped and point- cusp (0); absent or occasionally present as ing anteriorly (if D-shaped, rounded por- swelling on lingual side of protoconid (1) tion directed anteriorly) (1) (modi®ed (modi®ed from Zhou et al., 1995). from Gentry and Hooker, 1988). 103. M3 (ordered).ÐPresent, larger than M2 87. Lower canine.ÐConsists of a distinct (0); present, approximately equal (1); re- crown and root (0); hypsodont, no clear duced, maximum mesodistal length boundary between crown and root (1) Ͻ60% the length of M2 (2); absent (3) (Pickford, 1983). (modi®ed from Zhou et al., 1995; Geisler and Luo, 1998). PREMOLARS 104. M3 metaconid.ÐPresent, forms distinct cusp (0); absent or occasionally present as 88. P1 (ordered).ÐAbsent (0); present, one- swelling on lingual side of protoconid (1). rooted (1); present, two-rooted (2) (Zhou Cannot be scored for taxa that lack M3 et al., 1995; O'Leary, 1998a). (modi®ed from Zhou et al., 1995).

89. P1.ÐPresent (0); absent (1) (Zhou et al., 105. M3 hypoconulid (ordered).ÐLong, pro- 1995). trudes as separate distal lobe (0); reduced,

90. P1 morphology.ÐLow, transversely com- does not protrude substantially beyond pressed cusp (0); caniniform, single cusp rest of talonid (1); absent (2) (Thewissen, high and pointed (1); molariform, two 1994). main cusps in trigonid followed by com- 106. Parastyle or preparacrista position.Ð pressed talonid basin (2) (modi®ed from Lingual position, in line with or lingual Gentry and Hooker, 1988). to a line that connects the paracone or 91. P3 roots.ÐThree (0); two (1) (Zhou et al., metacone (0); labial position, labial to the 1995). line that connects the paracone and meta-

92. P3 metaconid.ÐAbsent (0); present (1) cone. (Thewissen and Domning, 1992). 107. Molars.ÐHave stylar shelves (0); stylar 93. P4 protocone.ÐPresent (0); absent (1) shelves absent (1). (Thewissen, 1994). 108. Ectocingula on upper molars.ÐPresent 94. P4 paracone.ÐEqual or subequal to (0); absent (1) (O'Leary, 1998a). height of paracone of M1 (0); greater than 109. Mesostyle on upper molars.ÐAbsent (0); twice the height of M1 paracone (1) present but much lower than paracone and (Thewissen, 1994). metacone (1); present and high with crests 95. P4 metacone.ÐAbsent (0); present (1). connecting to paracone and metacone (2). 96. P4 entocingulum.ÐPresent, partially or 110. Paraconule of upper molars (ordered).Ð completely surrounds the base of proto- Present (0); reduced (1); absent (2) cone (0); absent or very small (1). (O'Leary, 1998a). 97. P4 metaconid.ÐAbsent (0); present (1) 111. Number of cusps in posterolingual quad- (Thewissen and Domning, 1992). rant of M1 and M2 (ordered).ÐTwo, both 98. Deciduous P4.ÐResembles M1 (0); six- hypocone and metaconule present (0); cusped with additional neomorphic cusp one, hypocone or metaconule present (1); on paracristid (1) (derived from Gentry none, both hypocone and metaconule ab- and Hooker, 1988; Luckett and Hong, sent (2). 1998). 112. Protoloph.ÐAbsent (0); present (1) (Hooker, 1989). MOLARS 113. Metaloph.ÐAbsent (0); present (1) (Hooker, 1989). 99. M1 parastyle (ordered).ÐAbsent (0); 114. Lingual cingulid on molars.ÐPoorly de- 46 AMERICAN MUSEUM NOVITATES NO. 40

®ned or absent (0); continuous to mesial 128. Cervical vertebrae (ordered).ÐShort, to distal extreme (1) (O'Leary, 1998a). length shorter than centra of anterior thor- 115. Lower molar paraconid or paracristid po- acics (0); long, length of centrum greater sition.ÐCusp lingual or crest winds lin- than or equal to the centra of the anterior gually (0); cusp anterior or crest straight thoracics (1); very long, length closer to mesodistally on lingual margin (1) twice the length of the anterior thoracics (O'Leary, 1998a). (2) (derived from Gingerich et al., 1995).

116. M1 and M2 hypoconulid.ÐAbsent (0); 129. Arterial canal for vertebral artery in cer- present (1) (Gentry and Hooker, 1988). vical vertebrae 3±6.ÐPosterior openings 117. Crest connecting entoconid and hypocon- exterior to neural canal (0); inside neural id to the exclusion of the hypoconulid on canal (1) (Gentry and Hooker, 1988). lower molars (hypolophid).ÐAbsent (0); 130. Articulation between sacral vertebrae and present (1) (Gentry and Hooker, 1988). illium of pelvis (ordered).ÐBroad area of 118. Metastylid of lower molars.ÐAbsent (0); articulation between pelvis and S1 and present (1) (Gentry and Hooker, 1988). possibly S2 (0); narrow articulation of 119. Entoconulid of lower molars.ÐAbsent pelvis with end of transverse process of (0); present (1) (Gentry and Hooker, S1 (1); articulation absent (2) (Geisler and 1988). Luo, 1998). 120. Molar protoconid.ÐSubequal to height of 131. Number of sacral vertebrae (ordered).Ð talonid (0); closer to twice height of tal- One (0); two or three (1); four (2); ®ve or onid or greater (1) (O'Leary, 1998a). six (3). Cannot be scored for taxa that 121. Loph formation on anterior aspect of low- lack articulation of vertebral column to il- er teeth.ÐAbsent (0); present (1) (Hook- lium (Thewissen and Domning, 1992; er, 1989). Gingerich et al., 1995). 122. Reentrant grooves (ordered).ÐProximal (0); absent (1); distal (2) (Thewissen, FORELIMB 1994; O'Leary, 1998a). 123. Talonid basins.ÐBroad, hypoconid and 132. Scapular spine.ÐBears large acromion entoconid present (0); compressed, with process that overhangs glenoid fossa (0); hypoconid displaced lingually and cen- scapular spine with acromion process re- tered on the width of the tooth, entoconid duced or absent, does not encroach upon absent (1) (modi®ed from Zhou et al., glenoid fossa (1); acromion process un- 1995; description based on O'Leary and reduced, directed anteriorly and does not Rose, 1995a; Geisler and Luo, 1998). encroach upon the glenoid fossa (2) (derived from O'Leary and Rose, 1995b; OCCIPITAL CONDYLES AND VERTEBRAL O'Leary and Geisler, 1999). 133. Supraspinatus fossa of the scapula.Ð 124. Occipital condyles.ÐBroadly rounded in Large, portion on neck faces laterally and lateral view (0); V-shaped in lateral view, is equal to or larger than the infraspinatus in posterior view the condyle is divided fossa (0); small, portion on neck faces an- into a dorsal and a ventral half by a trans- terolaterally and is smaller than the infra- verse ridge (1). spinatus fossa (1). 125. Anteroventral border of occipital con- 134. Entepicondyle of humerus.ÐWide, width dyle.ÐTapers medially (0); ¯ared later- 50% or greater than the width of the ulnar ally and ventrally to form stop for ventral and radial articulation facets (0); narrow, movement of the cranium (1). 25% or less than the width of the ulnar 126. Odontoid process of axis.ÐForms ante- and radial articulation facets (1) (derived riorly pointed peg (0); spoutlike, dorsal from O'Leary and Rose, 1995b; Geisler surface forms concave trough (1); bears and Luo, 1998). central dorsal ridge that separates two 135. Entepicondylar foramen.ÐPresent (0); spoutlike troughs (2) (modi®ed from absent (1) (Thewissen and Domning, Webb and Taylor, 1980). 1992). 127. Atlantoid facet of axis vertebra.ÐRe- 136. Distal articular surface of humerus.ÐRe- stricted below neural arch or extends stricted by medial edge of trochlea (0); slightly dorsal to the base of the neural expanded medially past trochlear edge to pedicle (0); extended dorsally at least form convex surface (1) (Gentry and halfway up neural arch (1) (modi®ed from Hooker, 1988). Webb and Taylor, 1980). 137. Distal humerus intercondylar ridge be- 2001 GEISLER: ARTIODACTYLA, CETACEA, MESONYCHIDAE 47

tween capitulum and epicondyle.ÐAb- distal end of third phalanx terminates dis- sent (0); present (1) (modi®ed from Gen- tal to distal end of second phalanx of third try and Hooker, 1988). digit (0); reduced, distal end of third pha- 138. Length of olecranon process.ÐShort, lanx terminates proximal to distal end of Ͻ10% of total ulnar length (0); long, second phalanx of third digit (1); highly Ͼ20% of ulnar length (1) (derived from reduced, metacarpal forms proximal splint O'Leary and Rose, 1995b; O'Leary and or nodule (2); absent (3). Geisler, 1999). 150. Width of middle portion of ®fth metacar- 139. Posterior edge of ulna (ordered).ÐCon- pal (ordered).ÐWide, 100%Ͼ minimum vex posteriorly (0); straight (1); concave width of ®fth metacarpal Ͼ78% minimum posteriorly (2) (derived from O'Leary and width of third metacarpal (0); constricted, Rose, 1995b). 70%Ͼ minimum width of ®fth metacarpal 140. Radius and ulna (ordered).ÐCompletely Ͼ40% minimum width of third metacar- separate (0); fused distally (1); fused pal (1); highly compressed, 35%Ͼ mini- completely (2) (Webb and Taylor, 1980). mum width of ®fth metacarpal Ͼ15% 141. Proximal end of radius (ordered).ÐSin- minimum width of third metacarpal (2). gle fossa for edge of trochlea and capitulum of humerus (0); two fossae, for the HINDLIMB medial edge of the trochlea and the capitulum (1); three fossae, same as state 1 151. Greater trochanter of femur (ordered).Ð but with additional fossa for the lateral lip Below level of head of femur (0); approx- of the humeral articulation surface (2) imately same level as head of femur (1); (Geisler and Luo, 1998). elevated dorsally well beyond head of fe- 142. Distal articulation surface of radius.Ð mur (2) (derived from O'Leary and Rose, Single concave fossa (0); split into scaph- 1995b). oid and lunate fossae (1) (derived from 152. Third trochanter of femur (ordered).Ð O'Leary and Rose, 1995b; Geisler and Present (0); highly reduced (1); absent (2) Luo, 1998). (Luckett and Hong, 1998; O'Leary and 143. Centrale.ÐPresent (0); absent (1) (Thew- Geisler, 1999). issen, 1994). 153. Patellar articulation surface on femur.Ð 144. Magnum and trapezoid.ÐSeparate (0); Wide (0); narrow (1) (O'Leary and Geis- fused (1) (Webb and Taylor, 1980). ler, 1999). 145. Manus.ÐMesaxonic, axis of symmetry of 154. Tibia and ®bula (ordered).ÐSeparate (0); foot passes along center of digit three (0); fused proximally (1); fused proximally paraxonic, axis lies between digits three and distally (2) (Webb and Taylor, 1980). and four (1) (O'Leary and Geisler, 1999). 155. Fibula.ÐComplete (0); incomplete (1) 146. Second metacarpal contact with mag- (Webb and Taylor, 1980). num.ÐPresent (0); absent, excluded by 156. Proximal end of astragalus (ordered).Ð proximal end of metacarpal three (1). Nearly ¯at to slightly concave (0); well 147. Second digit of forelimb (ordered).Ð grooved, but depth of trochlea Ͻ25% its Long, distal end of third phalanx termi- width (1); deeply grooved, depth Ͼ30% nates distal to distal end of second pha- its width (2) (derived from Schaeffer, lanx of third digit (0); reduced, distal end 1947; O'Leary and Geisler, 1999). of third phalanx terminates proximal to 157. Astragalar canal.ÐPresent (0); absent (1) distal end of second phalanx of third digit (Shoshani, 1986). (1); highly reduced, metacarpal forms 158. Navicular facet of astragalus (ordered).Ð proximal splint or nodule (2); absent (3). Convex (0); saddle-shaped (1); V-shaped 148. Width of middle portion of second meta- (2) (Schaeffer, 1947; Thewissen and carpal (ordered).ÐWide, 130%Ͼ mini- Domning, 1992; Geisler and Luo, 1998). mum width of second metacarpal Ͼ94% 159. Distal end of astragalus contacts cuboid minimum width of third metacarpal (0); (ordered).ÐContact absent (0); contact constricted, 78%Ͼ minimum width of present, articulating facet on astragalus second metacarpal Ͼ51% minimum width forms a steep angle with the parasagittal of third metacarpal (1); highly com- plane (1); contact present and large, facet pressed, 36%Ͼ minimum width of second almost forms a right angle with the para- metacarpal Ͼ5% minimum width of third sagittal plane (2). metacarpal (2). 160. Long axes of proximal and distal articu- 149. Fifth digit of forelimb (ordered).ÐLong, lating surfaces of astragalus.ÐIf extrap- 48 AMERICAN MUSEUM NOVITATES NO. 40

olated, form angle that is obtuse and distal end of second phalanx of third digit opens medially (0); parallel, no angle (0); reduced, distal end of third phalanx formed (1) (modi®ed from Gentry and terminates proximal to distal end of sec- Hooker, 1988). ond phalanx of third digit (1); highly re- 161. Proximal half of lateral surface of astrag- duced, forms nodule or small splint (2); alus.ÐConcave (0); ¯at (1) (modi®ed absent (3); reduced, distal end of phalanx from Gentry and Hooker, 1988). terminates proximal to the distal end of 162. Lateral process of astragalus.ÐPresent, the second phalanx of the third digit be- ectal facet of the astragalus faces in the cause the second metatarsal is 50% of the plantar direction and its distal end points length of the third metatarsal (4). laterally (0); absent, ectal facet faces lat- 172. Width of the middle portion of the second erally and its long axis is parasagittal (1) metatarsal (ordered).ÐWide, 100%Ͼ (Schaeffer, 1947). minimum width of second metatarsal 163. Sustentacular facet of the astragalus.Ð Ͼ75% minimum width of third metatarsal Narrow and medially positioned, lateral (0); constricted, 68%Ͼ minimum width of margin of sustentacular facet of the as- second metatarsal Ͼ27% minimum width tragalus well medial to the lateral margin of third metatarsal (1); highly com- of the trochlea; (0) wide and laterally po- pressed, 18%Ͼ minimum width of second sitioned, lateral margin in line with the metatarsal Ͼ9% minimum width of third lateral margin of the trochlea (1) (derived metatarsal (2). from Schaeffer, 1947; Geisler and Luo, 173. Fifth digit of hindlimb (ordered).ÐLong, 1998). distal end of third phalanx terminates dis- 164. Sustentacular facet (ordered).ÐCom- tal to distal end of second phalanx of third pletely separated from navicular/cuboid digit (0); reduced, distal end of third pha- facet (0); medial edge of sustentacular lanx terminates proximal to distal end of facet continuous (1); completely contin- second phalanx of third digit (1); highly uous with cuboid/navicular facet (2). reduced, metatarsal forms nodule or small 165. Articulation of calcaneus and cuboid.Ð splint (2); absent (3). Flat, proximal articulating surface of the 174. Width of middle portion of ®fth metatarsal cuboid in one plane and corresponding (ordered).ÐWide, 100%Ͼ minimum surface of the calcaneus faces distally (0); width of ®fth metatarsal Ͼ70% minimum sharply angled and curved, proximal sur- width of third metatarsal (0); constricted, face of the cuboid has a distinct step be- 46%Ͼ minimum width of ®fth metatarsal tween the facets for the calcaneus and as- Ͼ36% minimum width of third metatarsal tragalus (1). (1); highly compressed, 26%Ͼ minimum 166. Cuboid and navicular.ÐUnfused (0); width of third metatarsal Ͼ10% minimum fused (1) (Webb and Taylor, 1980). width of third metatarsal (2). 167. Cubonavicular and ectocuneiform.ÐSep- 175. Elongation of third metatarsal.ÐAbsent, arate (0); fused (1) (Webb and Taylor, 20%Ͻ length of third metatarsal Ͻ39% of 1980). the length of the femur (0); slight elon- 168. Ectocuneiform and mesocuneiform.Ð gation, 47%Ͻ length of third metatarsal Separate (0); fused (1) (Webb and Taylor, Ͻ54% of the length of the femur (1); sub- 1980). stantial elongation, 63%Ͻ length of third 169. Pes.ÐMesaxonic, axis of symmetry of metatarsal Ͻ95% of the length of the fe- foot passes along center of the third digit mur (2). (0); paraxonic, axis lies between digits 176. Keels on distal ends of the metapodials.Ð three and four (1); axis passes along cen- Present, restricted to distal and plantar ter of digit four (2) (derived from Gin- surfaces (0); present and extended onto gerich et al., 1990; Thewissen, 1994; dorsal surface (or anterior surface in a O'Leary and Geisler, 1999). digitigrade stance) (1) (Webb and Taylor, 170. First metatarsal (ordered).ÐUnreduced, 1980). length Ͼ50% length of third metatarsal 177. Fusion of third and fourth metatarsals.Ð (0); reduced, length Ͻ50% length of third Absent (0); present (1) (Webb and Taylor, metatarsal (1); highly reduced, metatarsal 1980). forms nodule or small splint or is absent 178. Anterior surface of distal ends of third (2) (O'Leary and Geisler, 1999). and fourth metatarsals.ÐUnfused (0); 171. Second digit of hindlimb.ÐLong, distal fused, fusion forms prominent gully be- end of third phalanx terminates distal to tween third and fourth metatarsals (1) 2001 GEISLER: ARTIODACTYLA, CETACEA, MESONYCHIDAE 49

(Janis and Scott, 1987; Scott and Janis, STOMACH 1993). 179. Ventral edge of distal phalanges of 183. Right side of fornix ventriculi (or- foot.ÐDistinctly concave (0); ¯at (1) dered).ÐJust lateral to dorsal mesogastri- (O'Leary and Geisler, 1999). um (0); large, expanded anteriorly and 180. Distal phalanges of foot in dorsal view.Ð laterally (1); hypertrophied, forms elon- Phalanx compressed transversely (0); gate blind sac (2); forms elongate blind broad transversely, each phalanx is bilat- sac, and sac divided into compartments eral with central anteroposterior axis (1); by internal septa (3) (modi®ed from broad transversely, each phalanx is asym- Langer, 1974). metrical (2) (O'Leary and Geisler, 1999). 184. Omasum.ÐAbsent (0); present (1) (Lang- er, 1974).

INTEGUMENT OTHER SOFT TISSUE

181. Hair.ÐAbundant to common on body 185. Cavernous tissue of penis.ÐAbundant (0); almost completely absent (1) (Gatesy, (0); sparse (1) (derived from Slijper, 1997; O'Leary and Geisler, 1999). 1936; Thewissen, 1994). 182. Sebaceous glands.ÐPresent (0); absent 186. Primary bronchi of lungs.ÐTwo (0); (1) (Gatesy, 1997; O'Leary and Geisler, three, two on the right and one on the left 1999). (1) (Thewissen, 1994). 50 AMERICAN MUSEUM NOVITATES NO. 40 3. The matrix is avail- ϩ 2 ϩ 1 ϭ 3; I ϩ 1 ϩ 0 ϭ 2; H ϩ 1 ϩ 0 ϭ 4; G ϩ 3 ϭ 3; F ϩ 2 ϭ 2; E ϩ 1 ϭ 3; D ϩ 0 APPENDIX 3. CHARACTER CODINGS ϭ 2; C ϩ 0 ϭ 1; B ϩ 0 ϭ character inapplicable; A ϭ The 176 morphological characters were coded for 68 taxa. The observations are based on specimens and references listed in appendix 1. N able from http://herbaria.harvard.edu/treebase/ under study accession number S 589. 2001 GEISLER: ARTIODACTYLA, CETACEA, MESONYCHIDAE 51 Continued APPENDIX 3 52 AMERICAN MUSEUM NOVITATES NO. 40 Continued APPENDIX 3 2001 GEISLER: ARTIODACTYLA, CETACEA, MESONYCHIDAE 53 Continued APPENDIX 3 No RH this page!! novi 01219 Mp_54 File # 01TQ No RH this page!! Recent issues of the Novitates may be purchased from the Museum. Lists of back issues of the Novitates and Bulletin published during the last ®ve years are available at World Wide Web site http://nimidi.amnh.org. Or address mail orders to: American Museum of Natural History Library, Central Park West at 79th St., New York, NY 10024. TEL: (212) 769-5545. FAX: (212) 769- 5009. E-MAIL: [email protected]

a This paper meets the requirements of ANSI/NISO Z39.48-1992 (Permanence of Paper).