Anthony R. Friscia

Respiratory turbinates of canids and felids: a quantitative comparison

The respiratory turbinates of mammals are complex bony plates within the nasal chamber that are covered with moist epithelium and provide an extensive surface area for the exchange of heat and water. Given their functional importance, maxilloturbinate size and structure are expected to vary predictably among species adapted to different environments. Here the first quantitative analysis is provided of maxilloturbinate structure based on high-resolution computed tomography (CT) scans of the skulls of eight canid and seven felid species. The key parameters examined were the density of the maxilloturbinate bones within the nasal chamber and how that density varied along the air pathway. In both canids and felids, total maxilloturbinate chamber volume and bone volume increased with body size, with canids having c. 1.5–2.0 times the volume of maxilloturbinate than felids of similar size. In all species, the volume of the maxilloturbinates varies from rostral to caudal, with the peak volume occurring approximately midway, close to where airway cross-sectional area is greatest. Interspecific differences among canids or felids in maxilloturbinate density were not consistent with adaptive explanations, i.e. the densest maxilloturbinates were not associated with species living in arid or cold habitats. Some of the observed variation in maxilloturbinate form might reflect a need for both low- and high-resistance pathways for airflow under alternative conditions.

CHRONOLOGY AND SPATIAL DISTRIBUTION OF LARGE MAMMAL BONES IN PIT 91, RANCHO LA BREA

Abstract The Rancho La Brea tar pits represent a collection of Pleistocene fossils from an unusual sedimentary environment. A taphonomic analysis of a single tar seep, Pit 91, reveals a complex history of deposition and diagenesis for specimens found there. Radiometric dating of 46 bones from Pit 91 documents at least two episodes of deposition, one from 45,000 to 35,000 yr and another, shorter interval from 26,500 to 23,000 yr. Interestingly, the law of superposition was not upheld consistently in this case study, as some younger bones were found at a greater depth than older bones, implying that taphonomic time averaging took place. Bones are distributed as disarticulated elements in two large concentrations that span both depositional episodes. In general, long bones are oriented horizontally, with little or no preference for cardinal orientation. Degree of weathering or abrasion is not correlated with depth. Bone-on-bone contact (pit wear), however, increases with depth, suggesting possible compaction of bones through time. These results, combined with the disarticulation common to nearly all recovered specimens, suggest a postentrapment journey for the bones unique to asphalt deposits.

AN ACTUALISTIC EXPERIMENT TO DETERMINE SKELETONIZATION AND DISARTICULATION IN THE LA BREA TAR SEEPS

Abstract: The famous Rancho La Brea tar seeps of Southern California trapped thousands of Pleistocene and early Holocene vertebrates, preserving them as jumbled columns of millions of disarticulated bones. Previous work has contributed to a hypothetical entrapment scenario, however, it lacks detail in the period between the time the animals perished and the permeation of their bones with tar. Additionally, previous work has shown that skeletal elements moved apart from each other at least 1–3 meters but it is unclear whether this movement occurred near the surface of the tar, soon after submersion, or later after burial by sediment and compaction. To help answer these questions of disarticulation and transport, we conducted an actualistic experiment to record the progress of microbial succession and skeletonization of specimens in tar. We submerged dismembered bobcat (Lynx rufus) carcasses in an undisturbed tar seep and recorded the progress of microbial faunal changes and tissue decay. Microbial communities differed between tar environments and tissue decay, and changes in microbial communities across the stages of decay indicate rapid microbial succession, with the microbes most involved in the decay likely originating from the liquid surface tar. The minimum time to achieve clean bone was 40 days, from which we conclude that a surficial process may have been responsible for the movement of bones in the La Brea tar seeps.

Comparative ecomorphology and biogeography of Herpestidae and Viverridae (Carnivora) in Africa and Asia

This thesis concerns the evolution of African small carnivorans, with emphasis on East African Viverridae and Herpestidae (Carnivora, Mammalia). Viverridae and Herpestidae are two Old World feliform (belonging to the cat branch) carnivoran families with a confusing, and sometimes even misleading, taxonomic and systematic history, in addition to a scarce fossil record. A new genus and species from Fort Ternan, western Kenya, dated to ca 14 Mya (million years ago), was described and tentatively assigned to the Viverridae. The excellent preservation of this material has the potential to shed much light on the evolution of feliform carnivorans from Africa. The fossil record of Carnivora from Laetoli, a Pliocene hominid-bearing site in northern Tanzania, was also described and placed in an evolutionary context. The age of the fossil fauna from Laetoli ranges from 4.3 Mya to 2.5 Mya. The fossil material from this site is remarkable for two reasons: it is extensive in both number of taxa represented and amount of fossil material, especially of small carnivorans, and it is fossilized and preserved under aeolian conditions. In addition to these paleontological studies, two studies concerning extant Viverridae and Herpestidae were conducted. First, the phylogeography of the white-tailed mongoose, Ichneumia albicauda, (Herpestidae), was examined, with the tentative conclusion that its origin is southern African. Second, the ecomorphology and biogeography of African and Eurasian Viverridae and Herpestidae was analysed in order to investigate if these features can be used to help assess their evolutionary history in the absence of fossils. The pattern that emerges in this study is that the species of Viverridae and Herpestidae do not generally overlap in ecomorphology where they overlap geographically, which indicates considerable competitive interactions between the families in both Africa and Eurasia.

Hierarchy, Morphology, and Adaptive Radiation: a Test of Osborn's Law in the Carnivora

Henry Fairfield Osborn’s law of adaptive radiation was intended to explain the early proliferation of morphological and functional variation in diversifying clades. Yet, despite much theoretical development and empirical testing, questions remain regarding the taxonomic levels at which adaptive radiation occurs, the traits involved, and its frequency across the tree of life. Here, we evaluate support for this “early burst” model of adaptive radiation in 14 ecomorphological traits plus body mass for the extant mammalian order Carnivora. Strong support for an early burst adaptive radiation is recovered for molar grinding area, a key proxy for diet. However, we find no evidence for early burst–like dynamics in body mass or multivariate trait data, suggesting a decoupling of evolutionary modes among traits driven by dietary specialization. Furthermore, the signal of an early burst is only recovered for Carnivora, and not in family–level clades. The lack of support for the early burst model of morphological adaptive radiation in previous phylogenetic studies may be a consequence of focusing on the wrong traits at the wrong taxonomic levels. Osborn’s law predicted that adaptive radiation should be hierarchically structured, and the search for its signature and understanding of its prevalence will require a renewed focus on functional traits and their evolution over higher-level clades.

Fossil lemurs from Egypt and Kenya suggest an African origin for Madagascar’s aye-aye

In 1967 G.G. Simpson described three partial mandibles from early Miocene deposits in Kenya that he interpreted as belonging to a new strepsirrhine primate, Propotto. This interpretation was quickly challenged, with the assertion that Propotto was not a primate, but rather a pteropodid fruit bat. The latter interpretation has not been questioned for almost half a century. Here we re-evaluate the affinities of Propotto, drawing upon diverse lines of evidence to establish that this strange mammal is a strepsirrhine primate as originally suggested by Simpson. Moreover, our phylogenetic analyses support the recognition of Propotto, together with late Eocene Plesiopithecus from Egypt, as African stem chiromyiform lemurs that are exclusively related to the extant aye-aye (Daubentonia) from Madagascar. Our results challenge the long-held view that all lemurs are descended from a single ancient colonization of Madagascar, and present an intriguing alternative scenario in which two lemur lineages dispersed from Africa to Madagascar independently, possibly during the later Cenozoic.The fossil taxon Propotto was originally identified as a primate, but is currently widely interpreted as a bat. Here, the authors identify Propotto as a stem chiromyiform lemur and, based on phylogenetic analysis, suggest two independent lemur colonizations of Madagascar.

Ptolemaia from West Turkana, Kenya

Abstract New fossil material assigned to Ptolemaia cf. grangeri (Mammalia: Ptolemaida) from the late Oligocene site of Nakwai, West Turkana, Kenya, is described and discussed. Recovery of these specimens represents the first record of Ptolemaia from sub-Saharan Africa, and extends the known geographic range of members in this genus southward by about 3,000 km. The Nakwai collection is comprised of two maxillary fragments, a partial mandible with p3 and p4, and an edentulous jaw preserving alveoli for p2-m3. Results from comparisons involving the new material support previous work highlighting convergent similarities between members of Ptolemaia and aardvarks.