Elwyn L. Simons

Dental microwear texture analysis of two families of subfossil lemurs from Madagascar

This study employs dental microwear texture analysis to reconstruct the diets of two families of subfossil lemurs from Madagascar, the archaeolemurids and megaladapids. This technique is based on three-dimensional surface measurements utilizing a white-light confocal profiler and scale-sensitive fractal analysis. Data were recorded for six texture variables previously used successfully to distinguish between living primates with known dietary differences. Statistical analyses revealed that the archaeolemurids and megaladapids have overlapping microwear texture signatures, suggesting that the two families occasionally depended on resources with similar mechanical properties. Even so, moderate variation in most attributes is evident, and results suggest potential differences in the foods consumed by the two families. The microwear pattern for the megaladapids indicates a preference for tougher foods, such as many leaves, while that of the archaeolemurids is consistent with the consumption of harder foods. The results also indicate some intraspecific differences among taxa within each family. This evidence suggests that the archaeolemurids and megaladapids, like many living primates, likely consumed a variety of food types.

Astragalar Morphology of Afradapis, a Large Adapiform Primate From the Earliest Late Eocene of Egypt

The ∼37 million-year-old Birket Qarun Locality 2 (BQ-2), in the Birket Qarun Formation of Egypts Fayum Depression, yields evidence for a diverse primate fauna, including the earliest known lorisiforms, parapithecoid anthropoids, and Afradapis longicristatus, a large folivorous adapiform. Phylogenetic analysis has placed Afradapis as a stem strepsirrhine within a clade of caenopithecine adapiforms, contradicting the recently popularized alternative hypothesis aligning adapiforms with haplorhines or anthropoids. We describe an astragalus from BQ-2 (DPC 21445C), attributable to Afradapis on the basis of size and relative abundance. The astragalus is remarkably similar to those of extant lorises, having a low body, no posterior shelf, a broad head and neck. It is like extant strepsirrhines more generally, in having a fibular facet that slopes gently away from the lateral tibial facet, and in having a groove for the tendon of flexor fibularis that is lateral to the tibial facet. Comparisons to a sample of euarchontan astragali show the new fossil to be most similar to those of adapines and lorisids. The astragali of other adapiforms are most similar to those of lemurs, but distinctly different from those of all anthropoids. Our measurements show that in extant strepsirrhines and adapiforms the fibular facet slopes away from the lateral tibial facet at a gradual angle (112-126°), in contrast to the anthropoid fibular facet, which forms a sharper angle (87-101°). Phylogenetic analyses incorporating new information from the astragalus continue to support strepsirrhine affinities for adapiforms under varying models of character evolution.

NEW REMAINS OF EOCENE AND OLIGOCENE AFROSORICIDA (AFROTHERIA) FROM EGYPT, WITH IMPLICATIONS FOR THE ORIGIN(S) OF AFROSORICID ZALAMBDODONTY

Abstract Molecular estimates for the divergence of Chrysochloridae (golden moles) and Tenrecoidea (tenrecs) date back to near the K-T boundary, but at present the oldest undoubted fossil members of these clades are early Miocene in age (∼20 Ma). The only Paleogene African genus that has been proposed as a possible stem tenrecoid is late Eocene (∼34 Ma) Widanelfarasia from Egypt, heretofore known only from the lower dentition. Here we employ high-resolution computed tomography to reveal the morphology of the maxillary post-canine dentition of Widanelfarasia, and describe fragmentary dental and mandibular remains of early Oligocene Jawharia (gen. nov.) and Eochrysochloris (gen. nov.). The upper molar dentition of Widanelfarasia provides evidence for an intermediate morphological stage between moderate dilambdodonty and incipient zalambdodonty. Phylogenetic analysis employing the morphological character matrix of Asher and Hofreiter (2006) places Widanelfarasia within crown Tenrecoidea, but an alternative placement of that genus as a stem tenrecoid could not be statistically rejected. Additional support for the latter hypothesis, and for the hypothesis of convergent evolution of zalambdodonty within Afrosoricida, is provided by Eochrysochloris gen. nov., which shares apomorphic premolar features with Miocene Prochrysochloris and extant chrysochlorids, but retains a well-developed talonid basin on its lower molars. Jawharia gen. nov. is interpreted as an advanced stem tenrecoid that provides additional support for the hypothesis that tenrecoid zalambdodonty evolved from moderate dilambdodonty. Some of the apomorphic morphological features shared by Widanelfarasia and early Miocene Protenrec are also seen in Todralestes, from the oldest (late Paleocene) placental mammal-bearing locality in Africa. As such Todralestes may be a stem or crown afrosoricid, and, if so, the oldest known Afro-Arabian member of Afrotheria.

A large-bodied anomaluroid rodent from the earliest late Eocene of Egypt: phylogenetic and biogeographic implications

ABSTRACT A new genus and species of anomaluroid rodent, Kabirmys qarunensis, is described based on isolated teeth, partial mandibles, and an edentulous partial maxilla from the earliest late Eocene Birket Qarun Locality 2 (BQ-2) in the Fayum Depression of northern Egypt. Kabirmys is the largest known Paleogene anomaluroid, with first lower molar area being about 2.5 times that of the roughly contemporaneous Nementchamys and Pondaungimys from Algeria and Myanmar, respectively. The genus exhibits distinctive features not seen in other Paleogene taxa, such as a complete mure, weak neo-endoloph, and open lingual sinus on the upper molars; Kabirmys lacks the complex enamel crenulations seen in Nementchamys and Pondaungimys. Phylogenetic analysis of dental features nests Kabirmys within crown Anomaluridae as a sister taxon of Nementchamys and Pondaungimys, but parsimony analysis following addition of a chronobiogeographic character places all of these taxa as basal stem members of Anomaluridae. This new evidence indicates that there was considerable diversity in body size and molar morphology among African anomaluroids near the middle-late Eocene boundary, and suggests that the group had an ancient origin on that landmass. Kabirmys shares some primitive features with the possible zegdoumyid ‘Glibia’ namibiensis from the Paleogene of Namibia, and suggests that anomaluroids might be derived from a zegdoumyid-like ancestor. The disappearance of anomaluroids in the upper (latest Eocene to early Oligocene) levels of the Fayum succession might be related to global cooling through the later Paleogene, which might have removed suitable habitats from northern Africa.

A primitive hyracoid (Mammalia, Paenungulata) from the early Priabonian (Late Eocene) of Egypt

A new hyracoid genus and species, Dimaitherium patnaiki from the early Late Eocene (early Priabonian) Birket Qarun Formation in the Fayum Depression, Egypt, is described. The material is approximately 37 million years old and three million years older than any other hyracoid known from the Fayum area. A partial cranium preserves features that are likely primitive within Paenungulata, such as a postorbital process made up solely of the frontals (without a parietal contribution), a restricted jugal contribution to the anterior orbital margin, and an anteriorly positioned orbit. The internal mandibular fenestra, a peculiar feature seen in many younger Fayum hyracoids, is primitively absent in Dimaitherium, but a coronoid canal is present at the base of the ascending ramus as in later hyracoids. The dentition of Dimaitherium shows several primitive characteristics, such as poorly molarised premolars, but otherwise differs little from many younger hyracoids. Phylogenetic analysis consistently places younger hyracoids, including procaviids, in a clade to the exclusion of Dimaitherium and the much older Seggeurius and Microhyrax. Given the phylogenetic hypotheses proposed here, the presence of ‘broken’ hypocristids on the lower molars is likely to have evolved more than once during hyracoid evolution. Evidence from the humerus, astragalus and calcaneum indicate that Dimaitherium may have been an agile climber, and was likely capable of rapid movement but was not cursorially adapted. Of the other two small Fayum hyracoids, Dimaitherium was more similar to Thyrohyrax than to Saghatherium. The presence of only this single genus and species in the Birket Qarun localities cannot be explained by depositional biases, and makes an ancient origin for the Fayum hyracoid lineages unlikely. The poorly known large-bodied Early Eocene hyracoids ‘Megalohyrax’ gevini and ‘Titanohyrax’ mongereaui and tantulus from Algeria and Tunisia were not placed with Fayum species of Megalohyrax or Titanohyrax in our phylogenetic analyses. It is unlikely that these species belong to those genera and provide no compelling evidence for an Early Eocene or Paleocene divergence of the Fayum hyracoid lineages.

New Oligocene Ptolemaiidae (Mammalia: ?Pantolesta) from the Jebel Qatrani Formation, Fayum Depression, Egypt

ABSTRACT A new species of Ptolemaia and two new species of a new genus, Cleopatrodon, are added to the scanty record of the exotic African Oligocene mammalian family, the Ptolemaiidae. Current evidence suggests the presence of at least two lineages (Ptolemaia and Cleopatrodon-Qarunavus) within the family during the Oligocene in Egypt. To the extent that this is correct, these lineages were at first divergent, then convergent, in certain aspects of their lower molar anatomy. The origin of the Ptolemaiidae, although almost certainly African, is obscure; they were considered to be in some way related to the Pantolestidae by many earlier workers and are retained provisionally in the suborder Pantolesta on dental characters shared with generalized members of that group. Although most of these might well be symplesiomorphous, they might betray as well a common though unknown origin with pantolestan mammals.

Cranial morphology of Thyrohyrax domorictus (Mammalia, Hyracoidea) from the early Oligocene of Egypt

Abstract The Jebel Qatrani Formation in the Fayum Depression, Egypt, has yielded a diverse hyracoid fauna that includes both small- and large-bodied forms. Thyrohyrax domorictus is one of the most common hyracoids found in the upper sequence of the Formation, from sites dating to between 29 and 31 Ma. The dental morphology of T. domorictus is more similar to that of living hyraxes than other Paleogene species, but additional morphological evidence is needed to test the hypothesis of procaviid affinities. Two fairly complete crania of T. domorictus are now known and provide a number of additional craniofacial characters for phylogenetic analysis. The specimens are comparable in size to other small-bodied Fayum hyracoids and extant procaviids. T. domorictus has a relatively long rostrum that is perforated by a nasomaxillary fossa, which is also present in Miocene Afrohyrax and Prohyrax and older Thyrohyrax pygmaeus. The anterior border of the orbit is positioned above the molars, and the orbital aperture is closed posteriorly by a complete postorbital bar. Compared to other Fayum hyracoids, T. domorictus exhibits relatively derived, and more procaviid-like, cranial morphology. The cranium of T. domorictus is most similar to that of the extant genus Dendrohyrax, and they share similar morphology of the orbit and cranial roof. Phylogenetic analysis including morphological and molecular data from a large sample of living and extinct afrotherians places Thyrohyrax domorictus as the closest known Paleogene relative of Procaviidae and Pliohyracidae, supporting the hypothesis of procaviid affinities that was originally proposed solely on the basis of dental morphology.