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A new fossil site in a previously unexplored part of western Madagascar (the Beanka Protected Area) has yielded remains of many recently extinct vertebrates, including giant lemurs (Babakotia radofilai, Palaeopropithecus kelyus, Pachylemur sp., and Archaeolemur edwardsi), carnivores (Cryptoprocta spelea), the aardvark-like Plesiorycteropus sp., and giant ground cuckoos (Coua). Many of these represent considerable range extensions. Extant species that were extirpated from the region (e.g., Prolemur simus) are also present. Calibrated radiocarbon ages for 10 bones from extinct primates span the last three millennia. The largely undisturbed taphonomy of bone deposits supports the interpretation that many specimens fell in from a rock ledge above the entrance. Some primates and other mammals may have been prey items of avian predators, but human predation is also evident. Strontium isotope ratios (87Sr/86Sr) suggest that fossils were local to the area. Pottery sherds and bones of extinct and extant vertebrates with cut and chop marks indicate human activity in previous centuries. Scarcity of charcoal and human artifacts suggests only occasional visitation to the site by humans. The fossil assemblage from this site is unusual in that, while it contains many sloth lemurs, it lacks ratites, hippopotami, and crocodiles typical of nearly all other Holocene subfossil sites on Madagascar.
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CHARACTERIZING TRANSPORT IN HADROSAUROID DINOSAURS: AN ACTUALISTIC EXPERIMENTAL APPROACH TO FLUVIAL TAPHONOMY
Taphonomic processes create bias in the fossil record, and understanding these processes is integral to interpreting the record of extinct life worldwide. Bones preserved in fluvial environments make up a substantial part of the vertebrate fossil record. These bones have often been transported varying distances from the location of death before becoming buried. Experiments in flumes and natural settings have explored the fluvial taphonomy of mammal skeletons, but the taphonomy of other terrestrial vertebrates, especially extinct clades, has only been sparingly studied directly. Hadrosauroids are a dinosaur clade known from extensive remain throughout the Cretaceous and across the globe, making them an ideal group for taphonomic study. Previous examinations regarding the fluvial taphonomy of their skeletons have often applied bone transport groups derived from classic studies on mammals. Some researchers have raised concerns that the morphologies of non-mammalian bones would not exhibit the same hydraulic properties as mammals, producing different transport patterns. Here, we investigate hadrosauroid bone transport under various flow conditions through actualistic flume experiments using 3d printed models with comparable densities to real bone. We aimed to characterize the timing of transport of different elements (Voorhies Groups), orientation of bones relative to flow direction, and bone surface abrasion patterns. Some elements behave similarly to those described in mammals. As would be expected from previous work, relatively heavy bones such as the femur tend to move last, acting as lag elements. Lighter elements such as the scapula and radius tended to begin moving at much lower flow speeds. Because dinosaur pelvic bones are not fused as in mammals, we observed that the isolated pubis is often among the first elements to commence movement, often rotating or sliding along the bed. Cylindrical limb bones tend to roll or slide along the bed, orienting to be parallel to flow faster or slower depending on element size and flow velocity. Bones with more complex shapes, such as the curved and concave blade of the scapula, moved in less straightforward and unique ways, even vaulting over other bones. We also found that burial by fine silt and mud could be achieved relatively quickly even at slower flow speeds, and burial by sand played an important part in inhibiting transport in higher flow regimes.
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- Award ID(s):
- 1925884
- PAR ID:
- 10483581
- Publisher / Repository:
- Society of Vertebrate Paleontology
- Date Published:
- Journal Name:
- Journal of Vertebrate Paleontology, Program and Abstracts, 2023, P117
- Format(s):
- Medium: X
- Location:
- Cincinnati, OH
- Sponsoring Org:
- National Science Foundation
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