Earth:Reeve's Bonebed

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Short description: Fossil-rich formation in Texas

Reeve's Bonebed is a geological formation in Presidio County, Texas , with the coordinates of 29.9° N, 104.2° W. It consists of fossiliferous sedimentary rock dating from the late Eocene and early Oligocene. It is well known for its vertebrate fossils, hence the name "bone bed". A few invertebrate fossils are also present.

Geology

Reeve's bonebed lies in the Vieja Formation.

Ecology

The University of Texas has a large collection of fossils from Reeve's Bonebed which represent numerous different taxonomic groups. In the following table, the number of specimens of each taxon in the university collection from the bonebed is indicated in the abundance column:[1]

Mammals

Order Family Genus/Species Abundance (?/870) Notes

Cetartiodactyla

Merycoidodontidae

Merycoidodon

91: common

Bathygenys

709: extremely common

hundreds of endocasts (see below)

Leptomerycidae

Hendryomeryx defordi

2: extremely rare

Leptomeryx

10: rare

Oromerycidae

Eotylopus reedi

1: extremely rare

Agriochoeridae

Agriochoerus

15: average abundance

Protoceratidae

Leptotragulus

1: extremely rare

Heteromeryx defordi

2: extremely rare

Rodentia

Eutypomyidae

Eutypomys inexpectatus

13: average abundance

Ischyromyidae

Pseudotomus johanniculi

1: extremely rare

holotype

Leptotomus

1: extremely rare

Cylindrodontidae

Ardynomys

1: extremely rare

Cylindrodon fontis

3: extremely rare

Perissodactyla

Tapiridae

Colodon

4: rare

Equidae

Mesohippus

11: average abundance

Hyracodontidae

Hyracodon primus

1: extremely rare

Brontotheriidae

Menodus bakeri

1: extremely rare

Carnivora

Miacoidea

Miacis cognitus

1: extremely rare

holotype

Creodonta

Hyaenodontidae

Hyaenodon

2: extremely rare

Other taxa

Additional fossils to which a genus cannot be assigned include:

  • gastropods (snails)
  • testudinata (turtles)
  • Pholidosteids (Placoderms, armored fish)

Oreodont braincasts

Reeve's Bonebed is known for the recovery of casts of the brain cavity (endocast) of oreodonts.[2] When an animal dies and the soft tissues decay, sediments fill the orifices of the bones including the brain case inside the skull. If the bone subsequently falls apart, a cast of the inside of the skull may remain intact. Hundreds of brain casts, mainly from Bathygenys, were recovered from Reeve's Bonebed. These casts have been used to gauge the size of the brain of these animals, as well as the size of the various brain lobes. The physical arrangement of the brain can give clues about the life of the living animal, such as how important smell was to it, as used in CT scans of Tyrannosaurus. Studies involving more than 150 of these endocasts have been performed from the Reeve's Bonebed samples.[3]

References

  1. University of Texas, Austin. "Reeves bonebed". Archived from the original on 2011-09-29. https://web.archive.org/web/20110929032524/http://www.npl.utexas.edu/vpl/databases/index.php?page=33&page_size=10&mode=search&action=search&searchtype=&taxon=&locality=Reeves. 
  2. "Oreodont braincasts". http://www.utexas.edu/tmm/exhibits/treasures/archive/oreodont_bcasts.html. 
  3. Macrini, Thomas E. (2009). "Description of a Digital Cranial Endocast of Bathygenys reevesi (Merycoidodontidae; Oreodontoidea) and Implications for Apomorphy-Based Diagnosis of Isolated, Natural Endocasts". Journal of Vertebrate Paleontology 29 (4): 1199–1211. doi:10.1671/039.029.0413.