Timothy J. Gaudin

The ear region of edentates and the phylogeny of the Tardigrada (Mammalia, Xenarthra)

ABSTRACT A cladistic investigation of the phylogenetic relationships among 21 extinct and extant genera of sloths (Mammalia, Xenarthra, Tardigrada) was performed on the basis of characteristics of the bony anatomy of the auditory region. This study was undertaken in order to evaluate specific hypotheses of relationship within the group. Questions of particular interest include the relationship among the three traditional family groupings of extinct ground sloths and the monophyletic or diphyletic origin of the two genera of extant tree sloths. Eighty-five discrete morphological characters were analyzed using the computer program PAUP. Characters were polarized via comparisons to the following successive outgroups, all members of the supraordinal grouping Edentata: the Vermilingua, or anteaters; the Cingulata, or armadillos and glyptodonts; the Palaeanodonta; and the Pholidota, or pangolins. Three most parsimonious trees result (for 21 ingroup taxa and 5 outgroup taxa; Length = 304 steps, CI = 0.405, RI = ...

Reexamination of the morphological evidence for the cohort Epitheria (Mammalia, Eutheria)

Novacek and co-workers recognized a monophyletic clade Epitheria, comprising all eutherians except edentates and the extinct palaeoryctoids, on the basis of two synapomorphies: a stirrupshaped stapes and a foramen ovale enclosed within the alisphenoid. To evaluate this phylogenetic hypothesis, we reexamined the distributions of stapedial morphologies and positions of the foramen ovale across Recent and extinct mammals and nonmammalian cynodonts. The states and distributions of the stapes and forament ovale characters used by Novacek and coworkers were modified by recognizing two stapedial characters (one relating to shape of the crura, the other to the nature of the foramen) and a single, multistate foramen ovale character (within, behind, and lateral to the alisphenoid). The taxon-character matrix used by Novacek (1989, 1992b), substituting our amended stapedial and foramen ovale characters and adding several previously unscored extinct taxa and three new characters, was subjected to a series of PAUP manipulations. Identified among the most parsimonious trees were three major topologies for the base of Eutheria: (1) a polytomy including an Edentata/Ungulata clade, (2) a polytomy with Edentata and Ungulata as separate clades, and (3) Edentata and (when included) Palaeoryctoidea as the successive outgroups to a monophyletic Epitheria. We conclude that topology 2 best reflects the current state of knowledge. An edentate/ungulate clade is supported by three characters (from the mastoid region and subarcuate fossa); however, other morphological studies require modification of the distributions of these characters in xenarthrans and bassal ungulates, thereby eliminating support for this clade. In nearly all manipulations, obtaining a monophyletic Epitheria required that one or two steps be added to the most parsimonious trees. When a monophyletic Epitheria was obtained, it was supported by a triangular stapes and, in some trees, the reappearance of a stapedial artery (lost earlier at the level of Recent therians) and a transpromontorial internal carotid artery. In the most parsimonious trees, a foramen ovale within the alisphenoid was an equivocal synapomorphy of Recent therians or cutherians, and a stapes with strongly convex crura (our state closest to the stirrup-shaped state of Novacek and co-workers) appeared independently within various eutherian lineages. The reduction or loss of the stapedial foramen was identified as an independent event in monotremes and within marsupials and various eutherian lineages.

The Phylogeny of Living and Extinct Pangolins (Mammalia, Pholidota) and Associated Taxa: A Morphology Based Analysis

The present study was undertaken in order to effect a comprehensive phylogenetic analysis of the order Pholidota, examining seven of the eight currently recognized extant species (absent is Manis culionensis, formerly recognized as a subspecies of Manis javanica) and nearly all the well-known fossil taxa, and employing a wide range of osteological characters from the entire skeleton. In addition, the relationship of pangolins to several putative early Tertiary relatives, including palaeanodonts and the enigmatic “edentate” Eurotamandua joresi, were investigated. The goal of the study was to improve understanding of the systematics and the biogeographic and evolutionary history of the pangolins. A computer-based cladistic analysis of phylogenetic relationships among seven extant species of pangolins, five extinct pangolin species (including all but one of the well-preserved taxa), as well as Eurotamandua and two genera of metacheiromyid palaeanodonts, Palaeanodon and Metacheiromys, was performed based upon 395 osteological characteristics of the skull and postcranial skeleton. Characters were polarized via comparison to the following successive outgroups: the basal feliform carnivoran Nandinia binotata and the hedgehog Erinaceus sp., a eulipotyphlan laursiatherian placental. A revised classification is presented based on the results of the analysis. The results support the monophyly of Pholidota and Palaeanodonta by providing new anatomical characters that can serve to diagnose a pangolin/palaeanodont clade, termed here Pholidotamorpha. Pholidota is defined so as to include all living and fossil pangolins, including all three taxa of middle Eocene “edentates” from the Messel fauna of Germany, among them Eurotamandua joresi. The results do not support the monophyly of the remaining two Messel “edentates” originally placed in the same genus Eomanis, which is restricted to the type species Eomanis waldi. Euromanis, new genus, is named with Eomanis krebsi Storch and Martin, 1994, as the type species, to form a new combination Euromanis krebsi (Storch and Martin, 1994). The analysis strongly supports the monophyly of a crown clade of pangolins diagnosed by many anatomical synapomorphies, the family Manidae. This crown clade is sister to the family Patriomanidae, which includes two Tertiary taxa, Patriomanis americana and Cryptomanis gobiensis, within the superfamily Manoidea. The relationship of the Tertiary European pangolin Necromanis to these two families is unresolved. Within Manidae, the extant species are divided into three well-supported, monophyletic genera, Manis for the Asian pangolins, Smutsia for the African ground pangolins, and Phataginus for the African tree pangolins. The latter two form a monophyletic African assemblage, the subfamily Smutsiinae. The biogeographic implications of this phylogeny are examined. A European origin for Pholidota is strongly indicated. The fossil record of pangolins would seem to support a European origin for the modern forms, with subsequent dispersal into sub-Saharan African and then to southern Asia, and the phylogeny produced in this analysis is consistent with such a scenario.

The Phylogeny of the Myrmecophagidae (Mammalia, Xenarthra, Vermilingua) and the Relationship of Eurotamandua to the Vermilingua

A cladistic investigation of the phylogenetic relationships among the three extant anteater genera and the three undoubted extinct myrmecophagid genera is performed based upon osteological characteristics of the skull and postcranial skeleton. One hundred seven discrete morphological characters are analyzed using the computer program PAUP. Characters are polarized via comparison to the successive xenarthran outgroups Tardigrada (represented by the living sloth Bradypus) and Cingulata (represented by the recent armadillos Dasypus and Euphractus). The analysis results in a single most-parsimonious tree (TL = 190, CI = 0.699, RI = 0.713). The tree corroborates the monophyly of the subfamilies Cyclopinae and Myrmecophaginae, the former including the extant Cyclopes and the Pliocene genus Palaeomyrmidon. Within the Myrmecophaginae the Miocene genus Protamandua is the sister taxon to a clade including the remaining three genera. The recent Tamandua is in turn the sister taxon to the extant Myrmecophaga plus the Pliocene genus Neotamandua. Contrary to the suggestions of recent authors, weak support is provided for the taxonomic distinctiveness of the latter genus from the recent Myrmecophaga. The monophyly of the Myrmecophagidae is supported by 15 unequivocal synapomorphies. The monophyly of the Cyclopinae and Myrmecophaginae is supported by 3 and 13 unambiguous synapomorphies, respectively. The enigmatic Eocene genus Eurotamandua, from the Messel fauna of Germany, is coded for the 107 morphological characters above and included in two subsequent PAUP analyses. The palaeanodont Metacheiromys is also added to these two analyses as a nonxenarthran outgroup to test for the possibility that Eurotamandua lies outside the Xenarthra. In the first analysis, Eurotamandua is constrained a priori to membership in the Vermilingua. The single most-parsimonious tree (TL = 224, CI = 0.618) that results places Eurotamandua as the sister group to the remaining anteater genera, contra Storch and Habersetzers (1991) assignment of Eurotamandua to the vermilinguan subfamily Myrmecophaginae. Eurotamandua shares six unequivocal synapomorphies with other anteaters, including the absence of teeth and the presence of a lateral tuberosity on the fifth metatarsal. The remaining vermilinguans are united by 11 unequivocal synapomorphies, plus an additional 10 ambiguous synapomorphies. In the second analysis, the position of Eurotamandua is unconstrained. The resulting single most-parsimonious tree (TL = 219, CI = 0.632) places Eurotamandua outside Vermilingua as the sister group to the Pilosa (Vermilingua plus Bradypus). The monophyly of this node is supported by four unambiguous synapomorphies in the unconstrained analysis. Further manipulation of this second analysis shows that placement of Eurotamandua as the sister group to the Xenarthra or to the Palaeanodonta adds three steps to the shortest tree but is more parsimonious than its placement as a sister group to the Vermilingua is the previous analysis. The addition of pangolins to the analysis does little to alter the major phylogenetic conclusions of the study. The allocation of Eurotamandua to the Xenarthra, but as a sister group to the Pilosa, is a novel arrangement which leaves open the biogeographic question of how a xenarthran reached Western Europe during the Eocene.

Paleogene Xenarthra and the Evolution of South American Mammals

Recent studies show Xenarthra to be even more isolated systematically from other placental mammals than traditionally thought. The group not only represents 1 of 4 primary placental clades, but proposed links to other fossorial mammal taxa (e.g., Pholidota, Palaeanodonta) have been contradicted. No unambiguous Paleocene fossil xenarthran remains are known, and Eocene remains consist almost exclusively of isolated cingulate osteoderms and isolated postcrania of uncertain systematic provenance. Cingulate skulls are unknown until the late middle Eocene, and the oldest sloth and anteater skulls are early Oligocene and early Miocene age, respectively; there are no nearly complete xenarthran skeletons until the early Miocene. Ecological reconstructions of early xenarthrans based on extant species and the paleobiology of extinct Neogene taxa suggest the groups progenitors were myrmecophagous with digging and perhaps some climbing adaptations. The earliest cingulates were terrestrial diggers and likely myrmecophagous but soon diverged into numerous omnivorous lineages. Early sloths were herbivores with a preference for forested habitats, exhibiting both digging and climbing adaptations. We attribute the rarity of early xenarthran remains to low population densities associated with myrmecophagy, lack of durable, enamel-covered teeth, and general scarcity of fossil localities from tropical latitudes of South America. The derivation of numerous omnivorous and herbivorous lineages from a myrmecophagous ancestor is a curious and unique feature of xenarthran history and may be due to the peculiar ecology of the native South American mammal fauna. Further progress in understanding early xenarthran evolution may depend on locating new Paleogene fossil sites in northern South America.

Recent Advances on Variability, Morpho-Functional Adaptations, Dental Terminology, and Evolution of Sloths

The occasion of the Xenarthra Symposium during the ICVM 9 meeting allowed us to reflect on the considerable advances in the knowledge of sloths made by the “X-community” over the past two decades, particularly in such aspects as locomotion, mastication, diet, dental terminology, intraspecific variation, sexual dimorphism, and phylogenetic relationships. These advancements have largely been made possible by the application of cladistic methodology (including DNA analyses) and the discovery of peculiar forms such as Diabolotherium, Thalassocnus, and Pseudoglyptodon in traditionally neglected areas such as the Chilean Andes and the Peruvian Pacific desert coast. Modern tree sloths exhibit an upside-down posture and suspensory locomotion, but the habits of fossil sloths are considerably more diverse and include locomotory modes such as inferred bipedality, quadrupedality, arboreality or semiarboreality, climbing, and an aquatic or semi-aquatic lifestyle in saltwater. Modern tree sloths are generalist browsers, but fossil sloths had browsing, grazing, or mixed feeding dietary habits. Discovery of two important sloth faunas in Brazil (Jacobina) and southern North America (Daytona Beach and Rancho La Brea) have permitted evaluation of the ontogenetic variation in Eremotherium laurillardi and the existence of possible sexual dimorphism in this sloth and in Paramylodon harlani. A new dental terminology applicable to a majority of clades has been developed, facilitating comparisons among taxa. An analysis wherein functional traits were plotted onto a phylogeny of sloths was used to determine patterns of evolutionary change across the clade. These analyses suggest that megatherioid sloths were primitively semiarboreal or possessed climbing adaptations, a feature retained in some members of the family Megalonychidae. Pedolateral stance in the hindfoot is shown to be convergently acquired in Mylodontidae and Megatheria (Nothrotheriidae + Megatheriidae), this feature serving as a synapomorphy of the latter clade. Digging adaptations can only be securely ascribed to scelidotheriine and mylodontine sloths, and the latter are also the only group of grazing sloths, the remainder being general browsers.

The Entotympanic of Pangolins and the Phylogeny of the Pholidota (Mammalia)

Entotympanics are independent elements present in the auditory bullae of various eutherians. An entotympanic has been reported for extant pangolins of the Order Pholidota, but the actual distribution of this element remains uncertain, in part, because it is a small, loosely attached structure that is often lost in macerated skulls. Consequently, it is unknown whether or not the entotympanic characterizes Pholidota primitively or has evolved within the group. This report addresses the morphology and distribution of the entotympanic among living and extinct pholidotans. An entotympanic occurs in the African pangolins Manis gigantea, M. temminckii, and in one specimen of M. tricuspis. In each, it is a small, nodular bone that occupies a distinct fossa primarily on the basioccipital, the presence of which allows us to assess the occurrence of an entotympanic even in specimens in which the bone has fallen out. Both the entotympanic and the basioccipital facet are lacking in the four remaining extant pangolin species and in the late Eocene pangolin Patriomanis. To assess the significance of this entotympanic distribution, a phylogenetic analysis of extant pangolins plus Patriomanis based on 67 cranial characters was performed. Four different outgroup analyses all resulted in the same single most parsimonious tree, in which the three extant Asian pangolins form a monophyletic clade and the four extant African pangolins fall into a paraphyletic assemblage. Optimization of the entotympanic distribution onto this tree results in two patterns, dependent on the outgroup choice. If Patriomanis is the sole outgroup to the extant pangolins, the entotympanic arises within pangolins as a synapomorphy of Manis gigantea and M. temminckii, convergently acquired in some M. tricuspis. If Xenarthra and Palaeanodonta are employed as outgroups, the entotympanic optimization is ambiguous: the pattern is either as above or the entotympanic is present primitively within Pholidota and lost secondarily in Patriomanis and a clade comprising M. tricuspis, M. tetradactyla, and the Asian forms.

A New Genus of Megalonychid Sloth (Mammalia, Xenarthra) from the Late Pleistocene (Lujanian) of Sierra De Perija, Zulia State, Venezuela

ABSTRACT A skull and a partial skeleton of a large late Pleistocene megalonychid sloth recovered from a cave on Cerro Pintado, Sierra de Perijá Mountain Range, a branch of the northern Andes, in Zulia State, Venezuela, is described as a new genus and species, Megistonyx oreobios. A cladistic analysis of the new taxon based on cranial characters indicates that it is closely related to Ahytherium, another late Pleistocene megalonychid from South America known from cranial remains, and suggests that there may have been at least two distinct clades within the family since the late Miocene. Megistonyx oreobios is one of a number of extinct sloth taxa found at high elevations in South America and suggests that many extinct sloth taxa were not as thermally sensitive as their modern relatives and were capable of living under colder climatic conditions.

A NEW GENUS AND SPECIES OF PANGOLIN (MAMMALIA, PHOLIDOTA) FROM THE LATE EOCENE OF INNER MONGOLIA, CHINA

Abstract A partial postcranial skeleton from the late Eocene of the Shara Murun region of northern China is described as a new genus and species of fossil pangolin, Cryptomanis gobiensis. Cryptomanis displays numerous diagnostic pangolin characteristics, including enrolled lumbar zygapophyses and fissured ungual phalanges. Like the anatomically similar North American Eocene pangolin Patriomanis, it retains primitive mammalian features such as a convex astragalar head and a prominent femoral third trochanter that are lost in extant pangolins. The systematic position of Cryptomanis within Pholidota is not unambiguously resolved. It is tentatively placed in the family Patriomanidae, which we restrict to Cryptomanis and the closely similar Patriomanis. Cryptomanis differs from modern pangolins in its more robust proximal limb elements, its lack of a greatly enlarged third manual digit, its slender tail, and its more elongate, grasping pedal digits. These traits suggest an animal well adapted for digging but with a tendency toward a semi-arboreal lifestyle. This new genus and species represents the oldest and most northerly Asian record of pangolins, and indicates that pangolins were widely distributed throughout Laurasia during the Eocene. It is consistent with a Laurasian origin for pangolins.

AN EARLY PLIOCENE PANGOLIN (MAMMALIA; PHOLIDOTA) FROM LANGEBAANWEG, SOUTH AFRICA

Abstract A fossil pangolin is described from the early Pliocene of Langebaanweg, South Africa. Morphological adaptations indicate that the specimen was not arboreal as are the living African species Manis tricuspis and M. tetradactyla, but was probably ground dwelling and may have engaged in a quadrupedal gait similar to that of the living representatives of the African species, Manis gigantea. In addition, it may have used its forelimbs for more extensive digging than does the living African Manis temminckii. The tail length, limb bone widths and proportions, and humeral morphology support the assignment of this specimen to Manis gigantea, making it the oldest known fossil representative of this species and the only confirmed fossil pangolin from South Africa.