Nikos Solounias

Advances in the Reconstruction of Ungulate Ecomorphology with Application to Early Fossil Equids

Abstract A new and greatly simplified methodology for the assessment of the dietary adaptations of living and fossil taxa has been developed which allows for microwear scar topography to be accurately analyzed at low magnification (35×) using a standard stereomicroscope. In addition to the traditional scratch and pit numbers, we introduce four qualitative variables: scratch texture, cross scratches, large pits, and gouges, which provide finer subdivisions within the basic dietary categories. A large extant comparative ungulate microwear database (809 individuals; 50 species) is presented and interpreted to elucidate the diets of extant ungulates. We distinguish three major trophic phases in extant ungulates: traditional browsers and grazers, two phases represented by only a few species, and a browsing-grazing transitional phase where most species fall, including all mixed feeders. There are two types of mixed feeders: seasonal or regional mixed feeders and meal-by-meal mixed feeders. Some species have results that separate them from traditional members of their trophic group; i.e., browsers, grazers, and mixed feeders. Duikers are unique in spanning almost the entire dietary spectrum. Okapia, Tapirus, Tragulus, and Moschus species have wear similar to duikers. Proboscideans fall in the browsing-grazing transitional phase, as do the two suids studied. The latter differ from each other by their degree of rooting. Archaic fossil equids spanning the supposed browsing-grazing transition were compared to extant ungulates. Two major clusters are discerned: (1) Hyracotherium has microwear most similar to that of the duiker Cephalopus silvicultor and was a fruit/seed eating browser. (2) Mesohippus spp., M. bairdii, Mesohippus hypostylus, Meso-Miohippus (a transitional form larger than M. bairdii), Parahippus spp., and Merychippus insignis differ from Hyracotherium and are most similar to the extant Cervus canadensis. Group (2) is characterized by fine scratches which are the result of C3 grazing, an initial phase of grazing in equids which most likely did not occur in open habitats. Finer differentiation of group (2) diets shows a dietary change in the expected direction (toward the incorporation of more grass in the diet) and follows the expected evolutionary transition from the Eocene to the Oligocene and early Miocene. Consequently, these equid taxa are reconstructed here as mixed feeders grazing on forest C3 grasses. The finer dietary differentiation shows a progressive decrease in the number of scratches and pits. Mesohippus has the most pits and scratches, followed by Parahippus, and then Merychippus (which has the least). The taxon incorporating the most grass into its dietary regime in this array is Merychippus. In Mesohippus-Parahippus versus Merychippus, differences in tooth morphology are major but microwear differences are slight.

Stable isotopic evidence from paleosol carbonates and fossil teeth in Greece for forest or woodlands over the past 11 Ma

Abstract Mio-Pliocene fluvial rocks containing buried paleosols are common in Greece and Turkey. We used the carbon and oxygen isotopic composition of pedogenic carbonates associated with these paleosols to estimate the proportion of C3 (trees, shrubs, and cool growing season grasses) and C4 (warm growing season grasses) plants once present on the landscape. Evidence from the paleosols in well-known fossil-bearing formations in the lower Axios Valley in Macedonia, and from Samos, Pikermi near Athens, and Rhodes all show that Mio-Pliocene vegetation was dominated by C3 plants, as the entire region is today. In addition, nearly all paleosols contained carbonate, indicating that mean annual pitation has remained under about 1 m/yr during the last 11 Ma. The carbon isotopic evidence thus precludes the presence of Serengeti-type C4 grasslands favored by summer precipitation, but permits C3 forest or grasses fed by winter rains, or forest with mixed seasonal precipitation. However, there is no evidence in the published palynological records from the region for abundant grasses. Given these lines of evidence, we suggest that dry forest and woodland (largely C3) dominated the vegetation of the region. C3 grasslands, if present, were probably of very restricted extent. This reconstruction is supported by carbon isotopic evidence from fossil teeth from Samos and from Pasalar in NW Turkey, and by published evidence on masticatory morphology of Turolian-age ruminants from Samos and Pikermi. Our findings imply that the classic fossil-bearing localities on Samos and at Pikermi, and from the lower Axios Valley in Macedonia were not open savannas, as has been previously suggested, but rather, woodlands or forests.

Patterns of faunal turnover and diversity in the Neogene Siwaliks of Northern Pakistan

Abstract The fluvial Neogene Siwalik formations of northern Pakistan contain a long and richly fossiliferous sequence of terrestrial vertebrate faunas in which patterns of faunal turnover and changes in diversity can be documented and analyzed for intervals having durations of 0.5 m.y. The complete sequence extends from circa 18.5 to 1 Ma, but the part between 18.5 and 5.5 Ma is best sampled, and most intervals within it are well represented. Thirteen orders of Siwalik mammals have been identified, with well-sampled intervals having 50 or more species. Most Siwalik mammals, however, are either rodents or artiodactyls. Bovids are the most common and most speciose of the larger mammals, while murid and “cricetid” rodents dominate the small mammal assemblages. Between 18.5 and 5.5 Ma species diversity varied considerably. Among artiodactyls and rodents the number of species first increased between 15 and 13 Ma and then fell. Data on stratigraphic ranges of rodents and artiodactyls show that faunal change in the Siwaliks was episodic, occurring during short intervals with high turnover followed by longer periods with considerably less change. Maxima of first appearances occurred at approximately 13.5 and 8.5 Ma, while maxima of last occurrences were at 12.5 and 8.0 Ma. Some of the observed faunal events can be correlated to climatic and environmental changes. The Middle Miocene diversification occurred during a period of global cooling, while the latest Miocene decline in diversity and increased turnover accompanied oxygen and carbon isotopic changes that correlate to globally increasing seasonality and aridity. Other correlations are ambiguous. The marked decrease in diversity and the major turnover events between 13 and 8 Ma do not correspond to known local or global events. The Neogene Siwaliks and Paleogene Bighorn-Crazy Mountains sequence in Wyoming and Montana share many similarities. They have equivalent levels of temporal resolution and similar levels of completeness of their fossil records. Siwalik ordinal abundance and diversity patterns differ markedly from those of the Paleogene, but generic, and probably species, diversity was approximately the same, although the Siwalik faunas may have been slightly less diverse. Over time, changes in diversity were of comparable magnitude, with monotonic trends persisting for more than 5 million years. The magnitude of faunal turnover was also similar, ranging from less than half to 3.5 times that expected. In both sequences faunal change appears to have been episodic, with strong pulses between intervals of low turnover. The Siwaliks, in contrast to the Paleogene sequence, may have had more distinct pulses and longer intervals between pulses. Neither sequence has peaks of first occurrences coinciding with peaks of last occurrences.

THE DIETS OF THE DROMOMERYCIDAE (MAMMALIA: ARTIODACTYLA) AND THEIR RESPONSE TO MIOCENE VEGETATIONAL CHANGE

Abstract The probable diets of members of the extinct ruminant family Dromomerycidae were determined via an assessment of gross anatomical correlates of feeding strategy, mesowear analysis, and microscopic scar topography of enamel surfaces of cheek teeth. Discriminant models derived from 108 extant ruminants of known diet were applied to fossil taxa to ascertain probable trophic habits in dromomerycids. Microwear and mesowear analyses of molar tooth wear supplemented this gross skull and tooth morphological assessment as a means of providing more direct and independent sources of evidence for the nature and potential shifts in diet within dromomerycid lineages. In general, estimations of diets obtained from the study of gross morphology correlated well with those obtained from wear patterns. However, this was not always the case, suggesting that independent means of dietary analysis are critical when attempting to reconstruct paleodiets. In addition, hypsodonty (relative molar crown height) proved to be problematic as a variable in determining the diet of these extinct taxa. Information obtained from gross morphology, microwear, and mesowear support the hypothesis that later species of the Dromomerycidae within the tribe Cranioceratini had a shift in diet toward coarser food materials as a response to a trend toward increasing aridity and a shift in vegetational structure in the late Miocene–early Pliocene of North America.

Tooth microwear analysis of Eotragus sansaniensis (Mammalia: Ruminantia), one of the oldest known bovids

ABSTRACT A comparative tooth micro wear data base was established and analyzed for seventeen extant ungulates (six browsing species, four mixed feeder species, and seven grazing species). The three dietary categories are clearly reflected by the microwear results. Browsers have more pits, fewer total scratches, and more cross scratches, while grazers have fewer pits, more total scratches, and fewer cross scratches. The data of the mixed feeders form bimodal distributions, consisting of a browsing group and a grazing group, indicating that they either graze or browse. The microwear values of E. sansaniensis clearly fall within the browsing domain and more specifically, closest to the browser Tragelaphus strepsiceros.

Dietary interpretation and paleoecology of herbivores from Pikermi and Samos (late Miocene of Greece)

Abstract A large sample of the Pikermi and Samos ungulates was examined by microwear analysis using a light stereomicroscope (561 extinct and 809 extant comparative specimens). The results were used to infer the dietary adaptations of individual species and to evaluate the Pikermian Biome ungulate fauna. Many of the bovids have wear consistent with mixed feeding, although a few mesodont taxa apparently enjoyed an exclusive browsing and or grazing diet. The giraffids spanned the entire dietary spectrum of browsing, mixed feeding, and grazing, but most of the three-toed horses (Hippotherium) were hypsodont grazers. The colobine monkey Mesopithecus pentelici displays microwear consistent with a mixed fruit and leaf diet most likely including some hard objects. Similar results were obtained from prior scanning electron microscopy microwear studies at 500 times magnification and from the light microscope method at 35 times magnification for the same species. Results show that diet can differ between species that have very similar gross tooth morphology. Our results also suggest that the Pikermian Biome was most likely a woodland mosaic that provided a diversity of opportunities for species that depended on browsing as well as species that ate grass. The grasses were most likely C3 grasses that would grow in shaded areas of the woodland, glades, and margins of water. The ungulate component of the Pikermi and Samos fauna was more species-rich and more diverse in diet than the ungulates observed in modern African forests, woodlands, or savannas, yet dietarily most similar to the ungulates found in woodland elements of India and to some extent of Africa. It is unlikely that the Pikermi and Samos ungulates inhabited dense forests because we find no evidence for heavy fruit browsing. Conversely, a pure savanna is unlikely because many mixed feeders are present as well as browsers. Extant woodland African species are morphologically and trophically very similar to the African savanna species. Therefore the evolution of grazing and of hypsodont morphology for Africa may have evolved within the Plio-Pleistocene woodlands of Africa. Our results show that major dietary and morphologic ungulate evolution may take place within woodlands rather than as a consequence of species moving into savannas both during the late Miocene of Pikermi and Samos and during the Pleistocene–Recent of Central Africa.

New interpretations of the systematics and palaeoecology of the Dorn-Dürkheim 1 hipparions (late Miocene, Turolian age [MN11]), Rheinhessen, Germany

The Turolian vertebrate locality of Dorn-Dürkheim is situated near the city of Mainz, SW-Germany. The mammalian fauna is significantly younger than most other late Miocene Central European faunas that have yielded an equally rich assemblage of hipparion remains. The Dorn-Dürkheim hipparion fauna consists of isolated teeth and postcranial skeletal elements. We use the Vallesian (MN9) samples ofHippotherium primigenium from Eppelsheim and Höwenegg (Germany) as standards for comparison. Based on cheek tooth occlusal dimensions and continuous variables of the astragali, we identify two clusters of dental and postcranial specimens. We argue that these two clusters belong to two populations of hipparions that differ from one another principally in their body size. We further investigate the populations from Eppelsheim (EPhP), the total of all Dorn-Dürkheim specimens (DDpPall) and the two sub-populations from Dorn-Dürkheim (DDhPri and DDhPsm) with respect to their dietary preferences. For this we use the microwear and mesowear methods. The paleodietary signals for each sub-population are found to be quite different. The larger sized population of Dorn-Dürkheim (DDhPri) was a mixed feeder, while the small sized population (DDhPsm) is interpreted to have been a dedicated browser. In addition, we redefine the calculation of indices of hypsodonty so that they are more appropriate to equine horses. In comparing the hypsodonty indices of the hipparion populations from Eppelsheim and the total of the Dorn-Dürkheim specimens we find no differences in hypsodonty. In our comparison of Dorn-Dürkheim metacarpal III’s (MC III’s) with MC III’ from other pertinent European localities, we find two MC III’s from Dorn-Dürkheim to be similar to the Höwenegg population ofH. primigenium. However, eight Dorn-Dürkheim specimens differ from the Höwenegg population in having a relatively expanded crista sagittalis and reduced lateral and medial condyles. The only complete Dorn-Dürkheim MC III is relatively longer than the those from the Höwenegg population. This leads us to conclude that the MC III morphology of the smaller sized sub-population from Dorn-Dürkheim (DDhPsm) exhibits an adaptation for more cursorial locomotion than the Höwenegg hipparions, while the larger sized sub-population ventured into less forested habitats and was less cursorial. Based on the peculiarities of metapodial build and of cheek tooth dimensions, we recognize the population DDhPsm from Dorn-Dürkheim as belonging to a new species of hipparionine horse,Hippotherium kammerschmitti. New species:Cormohipparion n. sp.,Hippotherium kammerschmitti n. sp.KurzfassungDie turolische Wirbeltierlokalität Dorn-Dürkheim liegt nahe von Mainz in Südwestdeutschland. Die Säugetierfauna ist deutlich jünger als die meisten übrigen obermiozänen mitteleuropäischen Faunen und hat ein reiches, überwiegend aus isolierten Zähnen und postcranialen Skelettelementen bestehendes Hipparionenmaterial geliefert. Als Referenz für Vergleiche wird das vallesische Fundgut vonHippotherium primigenium von den Lokalitäten Eppelsheim und Höwenegg herangezogen. Basierend auf den occlusalen Dimensionen der Backenzähne und den Abmessungen von Astragali und Metapodien werden zwei Gruppen dentaler und postcranialer Individuen identifiziert. Diese zwei Gruppen werden zu zwei verschiedenen Unterpopulationen hipparioner Pferde gestellt, die sich im wesentlichen durch ihre Körpergröße unterscheiden. In Bezug auf ihre Nahrungspräferenzen werden ferner die Populationen von Eppelsheim (EPhP), die Gesamtheit aller Dorn-Dürkheim-Individuen (DDhPall) sowie die zwei Unterpopulationen von Dorn-Dürkheim (DDhPri and DDhPsm) untersucht. Hierfür kommen die Mikrowear- und die Mesowearmethode zum Einsatz. Die großwüchsige Population von Dorn-Dürkheim (DDhPri) wird als Mischkostfresser (mixed feeder) erkannt, während die kleinwüchsige Population (DDhPsm) als ausgesprochener Konzentratselektierer (browser) interpretiert wird. In der vorliegenden Untersuchung wird ferner die Berechnung des Hypsodontie-Index neu definiert, um den besonderen Gegebenheiten der Equiden besser gerecht zu werden. Zwischen den Hipparion-Populationen von Eppelsheim und der Gesamtheit der Dorn-Dürkheim-Individuen bestehen keine Unterschiede im Hypsodontie-Index. Im Vergleich der Metacarpalia III (MC III) von Dorn-Dürkheim mit Hipparionen verschiedener europäischer Lokalitäten sind zwei MC III’s von Dorn-Dürkheim der Höwenegg-Population vonH. primigenium im Bau sehr ähnlich. Acht MC III’s von Dorn-Dürkheim zeigen jedoch eine verhältnismäßig ausgedehnte Crista sagittalis und reduzierte laterale und mediale Condylen. Das einzige vollständig erhaltene Metacarpale III von Dorn-Dürkheim ist im Verhältnis zur Höwenegg Population relativ lang gestreckt. Hieraus wird geschlossen, dass die eine Subpopulation von Dorn-Dürkheim (DDhPsm) eine Adaptation zeigt, die gegenüber den Höwenegg-Hipparionen auf verstärkte kursoriale Lokomotion verweist. Dem gegenüber war die großwüchsigere Subpopulation weniger cursorial adaptiert. Basierend auf den Besonderheiten im Bau der Metacarpalia und in den Abmessungen der Backenzähne wird die Population DDhPsm als eine neue Art hipparioner Pferde erkannt,Hippotherium kammerschmitti.

The Oldest Bovid from the Siwaliks, Pakistan

ABSTRACT Two new small-sized bovid species are described from the Miocene of Pakistan (Kamlial and Vihowa formations, about 18 Ma), based on associated dentitions and horn cores. Eotragus noyei, sp. nov. is probably ancestral to all younger Eotragus and the modern Boselaphini. E. noyei has a horn core which does not have a pronounced anterior concavity and posterior convexity seen in younger Eotragus species and it has primitive teeth with inclined buccal walls. The indeterminate genus and species from the Vihowa Formation has compressed, keeled horn cores and more advanced teeth with vertical buccal walls. The morphology of the horn cores suggests that this taxon could represent the earliest known member of the keeled Boselaphini. If this hypothesis is correct, we are witnessing the presence in Pakistan of the first split within the Boselaphini (keeled Miocene species versus Eotragus and modern taxa).

A New Method of Tooth Mesowear and a Test of it on Domestic Goats

Mesowear III is a new form of mesowear that uses separately the mesial and distal surfaces of enamel band 2 of the upper second molar to differentiate between a browsing and a grazing diet. The enamel band of browsers is flat and planar, in grazers it contains gouges and sub-facets which eventually become round. Mesowear III scores these shapes on a scale 1–4; score 1 represents the typical browser and score 4 represents a typical grazer. Differences in diet can also be studied by observing the junction between the mesial and distal side of the enamel band (j point); the j point is sharper and well defined in browsers, while it is rounder or non-existent in grazers. Wild browsers, grazers, and mixed feeders separate well using mesowear III. The wild taxa data were similar to mesowear III of experimental goats that were fed a controlled grazing or browsing diet (species of plants known). In addition, the browsing versus the grazing goat mesowear III signal becomes more distinct from each other by 40 days of feeding. Mesowear III so far gives a finer signal than previous mesowear (I and II).

Cranial restoration of Eotragus sansaniensis (Mammalia: Ruminantia), one of the oldest known bovids

ABSTRACT The shape of the cranium of the fifteen million year old (Astaracian, MN zone 6) Eotragus sansaniensis from Sansan most closely resembles that of Tetracerus quadricornis (Boselaphini) but also resembles that of Cephalophus natalensis (Cephalophini), while E. sansaniensis horn cores are most similar to those of Boselaphus tragocamelus (Boselaphini). Morphologically, E. sansaniensis is one of the most primitive bovids known and is placed in the Boselaphini.