Prithijit S. Chatrath

Ecomorphology and Behavior of Giant Extinct Lemurs from Madagascar

Inferring the behavior of extinct organisms is a formidable task, even under the best of circumstances (Rudwick, 1964; Stern and Susman, 1983; Kay, 1984; Thomason, 1995). Nevertheless, and in spite of inevitable complications and limitations, such inferences remain the ultimate goal of paleobiologists if we are to understand fossils as integrated organisms rather than isolated bones and atomized character states. In this chapter we attempt to breathe life back into the osteological remains of recently extinct (or “subfossil”) prosimian primates from the Quaternary of Madagascar. Subfossil lemurs provide many special opportunities to the optimistic functional morphologist, but they also present their own unusual set of complications and potential frustrations. Approximately one-third of Madagascar’s known primate species were driven to extinction in the late Holocene by the lethal interaction of aridification and human colonization (Burney, 1997; Dewar, 1997; Simons, 1997), including all taxa of large body size (> 9 kg). Two new extinct species from northern Madagascar (Babakotia radofilai and Mesopropithecus dolichobrachion) have been discovered and described in the last decade (Godfrey et al., 1990; Simons et al., 1995), and a third new species from the northwest will be diagnosed soon (Jungers et al., in prep.). Sixteen currently recognized subfossil species of Malagasy primates are represented in museum collections, most by numerous individuals, including a growing tally of specimens with associated craniodental and postcranial elements (e.g., MacPhee et al., 1984; Simons et al., 1992,Simons et al., 1995; Wunderlich et al., 1996). Table I summarizes the current taxonomy of the extinct lemurs. Aspects of morphology suggest that cheirogaleids are more closely related to galagos and lorises than to other Malagasy primates (Szalay and Katz, 1973; Cartmill, 1975; Schwartz and Tattersall, 1985; Yoder, 1992). Molecular results, as well as “total evidence” analyses that combine morphological and molecular data, argue instead that the Malagasy primates are probably monophyletic (Yoder, 1994,Yoder, 1996). Regardless of the placement of the cheirogaleids within strepsirrhines, the precise relationships among the various ancient clades of Malagasy primates remain somewhat fuzzy, even from a biomolecular perspective (Yoder, 1997; Yoderet al., 1999).

Past and Present Distributions of Lemurs in Madagascar

Holocene cave, marsh, and stream deposits on the island of Madagascar have yielded thousands of “subfossil” specimens that document recent megafaunal extinctions. Excavations conducted during the past 15 years of archaeological and paleontological sites in northern, northwestern and southwestern Madagascar have unearthed, in addition to new specimens of extinct lemurs and other megafauna, an abundance of bones of still-extant lemur species. These specimens, as well as specimens of extant lemurs from subfossil sites excavated in the early and mid-1900’s, prove that living lemur species once had much broader geographic ranges than they have today, and they help to explain the currently disjunct distributions of a number of species. This paper examines the pattern of distribution of extant primate species at subfossil sites, and compares recent to modern primate communities.

A Freshwater Ichthyofauna from the Late Eocene Birket Qarun Formation, Fayum, Egypt

ABSTRACT A collection of fossil fish teeth and other elements from Eocene deposits on the northshore of Birket Qarun, Fayum Depression, Egypt, is reported. This collection adds significantly to our knowledge, as it consists of material that was screened from the sediments, allowing collection of small teeth that represent taxa not previously reported from the Fayum. Previous collections from these sediments have concentrated on larger remains that generally represent elasmobranchs, which are marine species from deposits lower in the section. Most of this material, collected by screening at the Birket Qarun 2 (BQ-2) locality, represents fully freshwater fishes. It includes the first record of the mormyrid Gymnarchus in the Fayum Depression, which represents the oldest record for this group, known previously only from the late Miocene or younger deposits. Similarly, Mochokidae (Siluriformes) and Hydrocynus (Alestidae) remains from the site are the oldest record of these taxa. Other taxa recovered are the osteichthyans Polypterus (Polypteriformes), Protopterus (Dipnoi), and Parachanna (Channidae), and the chondrichthyans Hypolophodon cf. H. malembeensis (Dasyatoidea incert. fam.), Rhinoptera sherborni (Rhinopteridae), and Coupatezia wousteri (Dasyatoidea incert. fam.). A new ray, Coupatezia attiai, n. sp., Cook, is also described. These fishes confirm the freshwater influence at locality BQ-2 in the Birket Qarun Formation.

THE SUBFOSSIL OCCURRENCE AND PALEOECOLOGICAL SIGNIFICANCE OF SMALL MAMMALS AT ANKILITELO CAVE, SOUTHWESTERN MADAGASCAR

Abstract Small mammals are rarely reported from subfossil sites in Madagascar despite their importance for paleoenvironmental reconstruction, especially as it relates to recent ecological changes on the island. We describe the uniquely rich subfossil small mammal fauna from Ankilitelo Cave, southwestern Madagascar. The Ankilitelo fauna is dated to the late Holocene (∼500 years ago), documenting the youngest appearances of the extinct giant lemur taxa Palaeopropithecus, Megaladapis, and Archaeolemur, in association with abundant remains of small vertebrates, including bats, tenrecs, carnivorans, rodents, and primates. The Ankilitelo fauna is composed of 34 mammalian species, making it one of the most diverse Holocene assemblages in Madagascar. The fauna comprises the 1st report of the short-tailed shrew tenrec (Microgale brevicaudata) and the ring-tailed mongoose (Galidia elegans) in southwestern Madagascar. Further, Ankilitelo documents the presence of southwestern species that are rare or that have greatly restricted ranges today, such as Nasolos shrew tenrec (M. nasoloi), Grandidiers mongoose (Galidictis grandidieri), the narrow-striped mongoose (Mungotictis decemlineata), and the giant jumping rat (Hypogeomys antimena). A simple cause for the unusual small mammal occurrences at Ankilitelo is not obvious. Synergistic interactions between climate change, recent fragmentation and human-initiated degradation of forested habitats, and community-level processes, such as predation, most likely explain the disjunct distributions of the small mammals documented at Ankilitelo.

Femoral anatomy of Aegyptopithecus zeuxis, an early oligocene anthropoid.

Three partial femora from Quarries I and M of the early Oligocene Jebel Qatrani Formation in the Fayum of Egypt are attributed to Aegyptopithecus zeuxis on the basis of their appropriate size and anthropoid morphology. Compared with extant catarrhines, Aegyptopithecus is unusual in having a distinct gluteal tuberosity (third trochanter) and a relatively deep distal femoral articulation. In the estimated neck angle, Aegyptopithecus resembles arboreal quadrupeds rather than either leaping or suspensory primates. It seems likely that the femur of this species was relatively robust and short for its body mass. In aspects of its femoral anatomy, Aegyptopithecus is quite different from the parapithecid Apidium and more similar to Catopithecus from late Eocene deposits of the Fayum, and also to small hominoids from the Miocene of East Africa.

A new species ofMesopropithecus (Primates, Palaeopropithecidae) from Northern Madagascar

We diagnose new subfossil specimens belonging to the extinct palaeopropithecid, Mesopropithecus,from several caves at the Ankarana massif in northern Madagascar. They include three partial crania with mandibles, and the first vertebrae, ribs, clavicle, pelvis, ulna, and hand and foot bones of Mesopropithecusever found. Several other postcranial elements are known for this northern variant of Mesopropithecusand for previously described species from central and southern Madagascar. The new materials cannot be accommodated in either currently recognized species of this genus and are,hereby, given the name Mesopropithecus dolichobrachion. M. dolichobrachionis the second new species of extinct subfossil lemur to be found in the caves of Ankarana. It is unlike the two previously described species of this genus primarily in its larger size, different limb proportions, and aspects of its long bone morphology. Most notable is the fact that this is the only species of Mesopropithecuswith the forelimb longer than the hind limb— hence the name, the “long-armed” Mesopropithecus.Various characteristics place M. dolichobrachionphenetically closest (of species belonging to Mesopropithecus)to Babakotia radofilai, Archaeoindris,and Palaeopropithecus.If these similarities are derived specializations rather than primitive for palaeopropithecids, a new generic name will be required.

Earliest Record of a Parapithecid Anthropoid from the Jebel Qatrani Formation, Northern Egypt

A fifth anthropoid (= anthropoidean, simian or simiiform) genus and species from the late Eocene Fayum Quarry L-41, Abuqatrania basiodontos gen. et sp. nov., further augments the already remarkable primate diversity from this locality and provides the first convincing extension of the enigmatic family Parapithecidae into the oldest productive vertebrate fossil-bearing stratum of the Jebel Qatrani Formation. A.basiodontos exhibits no clear autapomorphies nor any apomorphies that are shared exclusively with any other parapithecid species, and it is most parsimoniously interpreted as the sister taxon of a Qatrania-Parapithecus-Apidium clade. Reevaluation of two contemporaries of A. basiodontos, Serapia and Arsinoea, suggests that neither genus should be ranked as a basal parapithecid. Serapia is more derived than primitive parapithecids in the morphology of the lower fourth premolar and exhibits greater overall similarity to Proteopithecus in cusp placement and the shape and proportions of its lower teeth; accordingly, we place Serapia in the family Proteopithecidae. Arsinoea is much more problematic and does not fit well with any hitherto known Afro-Arabian anthropoid group; we place this genus in a new anthropoid family, Arsinoeidae.

The Eocene Origin of Anthropoid Primates

One of the few previous attempts to model anthropoid origins emphasized apparent global climatic changes at the Eocene—Oligocene boundary (now placed at 34 MA) that may have served as the driving force for changes in primate geographic distribution southward and for the evolutionary origin of key new dietary and foraging adaptations (Cachel, 1979, 1981). The most recent proponent of the idea that anthropoid origin was a geologically sudden event associated with profound environmental change at the Eocene—Oligocene transition has been Gingerich (1993). In recent years, however, the view of the Eocene—Oligocene boundary as an important threshold for anthropoid origins has been supplanted by new interpretations based on research in geology and dating (Bown and Kraus, 1988; Van Couvering and Harris, 1991; Kap-pelman et al., 1992; Rasmussen et al, 1992; Gingerich, 1993), Afro-Arabian paleontology (de Bonis et al., 1988; Thomas et al., 1988, 1989, 1991; Simons, 1989, 1990, 1992; Godinot, Ghapter 10, this volume; Godinot and Mahboubi, 1992; Hartenberger and Marandat, 1992), and functional anatomy (Rasmussen and Simons, 1992). Evidence now demonstrates that the anthropoid clade underwent a significant radiation in the late Eocene of Africa, where prosimi-ans were apparently scarce, and that these early anthropoids did not differ appreciably from their prosimian contemporaries on other continents in basic dietary and sensory adaptations or in size.

A Miocene selachian fauna from Moghra, Egypt

The fossil bearing beds of Moghra, Egypt, have been well known for over 100 years, but the ichthyofaunas have not been examined since the early 1900s. Moghra, on the northern rim of the Qattara Depression, preserves early Miocene (18–17 Ma) fluvio-marine sediments with fossils of wood, invertebrates and vertebrates. The Moghra site is faunally similar to the Libyan Gebel Zelten site, at least in terms of the fossil mammals. The fossil-bearing localities in the Moghra Formation number about 40 and span a distance of about 50 km. There is likely more than one depositional environment represented. The fish previously reported from Moghra include two teleosts, Synodontis (Mochokidae) and Lates (Latidae), as well as the elasmobranchs, Pristis (Pristidae), Myliobatis (Myliobatidae) and Sphyrna (Sphyrnidae). Several more recent expeditions to the Moghra localities recovered abundant selachian remains. This rich assemblage included species from the genera Carcharias (Odontaspididae), Megaselachus (Otodontidae), Cosmopolitodus (Lamnidae), Hemipristis (Hemigaleidae), Galeocerdo and Carcharhinus (Carcharhinidae), Myliobatis (Myliobatidae), Pteromylaeus (Myliobatidae) and Aetobatis (Myliobatidae). With the additional taxa from these collections, we can build a more comprehensive understanding of the Moghra fauna and environment.

Agamid lizard (Agamidae: Uromastycinae) from the lower Oligocene of Egypt

Agamid lizards are currently found in Africa, Asia, the eastern Mediterranean region and Australia. Together with the Chamaeleonidae and some extinct basal forms, they comprise the Acrodonta, lizards with acrodont dentition. The Acrodonta have been suggested to have a Gondwanan origin, with the oldest members found in the Triassic of India. The first agamids are known from the Late Cretaceous of Asia, and the group is widely distributed in the northern hemisphere throughout much of the Paleogene. However, the fossil history of Acrodonta on the Afro-Arabian plate is extremely limited: a single jaw fragment bearing acrodont dentition, possibly attributable to Agamidae, has been reported from the Paleogene of Morocco, and material identified as agamid was reported from the Oligocene of Oman. We here add to the African record the first clear evidence of Agamidae, represented by several jaws with attached teeth from earliest Oligocene deposits of the Jebel Qatrani Formation in the Fayum Depression, Egypt. Characters of the teeth, including very rounded labial surface, shearing edges concave lingually, shearing tip crescentic and accessory cusps absent, are similar to those of Uromastyx. Species of Uromastyx currently inhabit the Saharan and Somalian regions of Africa and adjacent Arabia.