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

By N. Solounias, G. Semprebon. 2002

487 citations recorded by the source corpus.

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.

Subfields: Ecology, Ecology, Evolution, Behavior and Systematics, Paleontology

View Paper: https://www.semanticscholar.org/paper/a95152011a7a2d2ba7141864c30ae73af59ee09c

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Ecology

1. J. Scott
2. P. Ungar
3. C. Janis
4. F. Rivals
5. Thomas M. Kaiser
6. G. Merceron
7. A. Lister
8. C. Strömberg

In Ecology, Evolution, Behavior and Systematics

1. F. Rivals
2. C. Janis
3. P. Palmqvist
4. Thomas M. Kaiser
5. M. Mendoza
6. A. Lister
7. G. Merceron
8. M. Clauss

In Paleontology

1. J. Scott
2. C. Janis
3. F. Rivals
4. Thomas M. Kaiser
5. A. Lister
6. P. Ungar
7. C. Strömberg
8. Matthew C. Mihlbachler

Citations in the corpus

• Mammalian dental function and wear: A review (2015, unknown): “Indeed, some researchers began to return to low-magni fi cation light microscopy [156,157] because of the cost and effort associated with SEM analysis.”
• Evidence for geographic variation in the diets of late Pleistocene and early Holocene Bison in North America, and differences from the diets of recent Bison (2007, methodology): “Cross scratches are oriented somewhat perpendicularly to the majority of scratches observed on dental enamel (Solounias and Semprebon, 2002).”
• A New Method of Dental Microwear Analysis: Application to Extant Primates and Ouranopithecus macedoniensis (Late Miocene of Greece) (2005, background): “Recent studies on the dental microwear of ungulates and primates have focused on the direct quantification on dental casts using a light stereomicroscope (Solounias and Semprebon 2002; Semprebon et al., 2004).”
• Evolution of hypsodonty in equids: testing a hypothesis of adaptation (2006, background): “Moreover, microwear studies, which have provided vital diet information for extinct equids (e.g., Hayek et al. 1992; Solounias and Semprebon 2002), are not always reliable.”
• Estimating the body mass of extinct ungulates: a study on the use of multiple regression (2006, background): “This equid has usually been considered to be a grazer, because of its high degree of hypsodonty, but results obtained from dental microwear (Solounias & Semprebon, 2002) and carbon isotopes (MacFadden, Solounias & Cerling, 1999) have been interpreted as indicative of a mixed feeding or even a…”
• The species richness of Miocene browsers, and implications for habitat type and primary productivity in the North American grassland biome (2004, background): “When hypsodonty is combined with other morphological variables or observations of tooth wear, highly reliable reconstructions of ungulate diets are possible (Janis, 1995; Fortelius and Solounias, 2000; Solounias and Semprebon, 2002).”
• A COMPARISON OF THE DIETARY HABITS OF A LARGE SAMPLE OF THE PLEISTOCENE PRONGHORN STOCKOCEROS ONUSROSAGRIS FROM THE PAPAGO SPRINGS CAVE IN ARIZONA TO THE MODERN ANTILOCAPRA AMERICANA (2006, methodology): “Results are compared to those for the modern pronghorn, A. americana (data on the latter obtained from Solounias and Semprebon, 2002).”
• Dental Microwear Texture Analysis of Varswater Bovids and Early Pliocene Paleoenvironments of Langebaanweg, Western Cape Province, South Africa (2007, background): “2005a), to perissodactyls (e.g., Hayek et al. 1991; MacFadden et al. 1999; Solounias and Semprebon 2002; Kaiser and Solounias 2003), artiodactyls (e.”
• The Late Miocene paleoenvironment of Afghanistan as inferred from dental microwear in artiodactyls (2004, methodology): “Solounias and Semprebon (2002) pointed out that leaf-browsing species belong mainly to the lowest scratch range, whereas grazing species fall into the middle or highest scratch ranges.”