| Cacops Fossil range: Early Permian | |
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 Cacops aspidephorus skeleton. | |
| Scientific classification
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Dissorophoidea | |
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Dissorophidae | |
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Cacops | |
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Cacops is an extinct genus of dissorophid amphibians that is known from the Early Permian of Texas. It was about 40 cm (16 inches) long, with a heavily built skull and an enormous otic notch enclosed with a bony bar; indicating an enormous eardrum. Edwin Colbert suggests that perhaps it was a nocturnal animal like modern frogs. The body was short, and the back was protected by a double row of armour plates. The legs were strong and indicate a terrestrial animal, and the tail was short.
History of discovery[]
Cacops aspidephorus is the most famous dissorophid, in part due to a majority of its skeleton having been known for over a century. Over 50 specimens have been found in the Cacops Bone Bed in Baylor County, Texas, which is now flooded by the dammed Lake Kemp. However, many of the specimens are covered in calcite, which penetrates the bone tissue, resulting in poor preservation. "Trematopsis seltini" from the Vale Formation of Texas was originally described as a trematopid by Olson (1956) but was later synonymized with Cacops aspidephorus by Milner (1985).
Cacops morrisi is named in honor of Tony Morris, who discovered one of its two specimens. Many specimens have been found in the Dolese Brothers Limestone Quarry, near Richards Spur, Oklahoma. Cacops morrisi has a skull that differs from C. aspidephorus in having a snout that is slightly longer than its post-orbital region, a shorter distance between the orbit and the temporal emargination, and uncinate processes of the ribs.
Cacops woehri is named in honor of Daniel Woehr, who is an amateur collector of fossils. Specimens have been found in the Dolese Brothers Limestone Quarry, near Richards Spur, Oklahoma. Cacops woehri differs from C. aspidephorus and C. morrisi in many attributes, including a more shallow skull, more dorsally located orbits, and a narrow opening of its tympanic embayment. The contribution of the postparietals to the skull roof also appears to be shorter in C. woehri than in C. morrisi, while the occipital flanges are proportionately larger in C. woehri. More notable differences distinguishable from C. morrisi include: absence of lateral exposure of ectopterygoid in juveniles, absence of tusk-like teeth on the anterior margin of the interpterygoid vacuities, and the quadratojugal lacking an anterior process. The teeth of C. woehri are also not recurved as in C. aspidephorus and C. morrisi, showing instead a distinct lingual curvature. Because of the different skull shape, it is theorized that this specific taxon may have had a different ecology than its sister taxa, possibly with a different prey spectrum. This suggests that there could have been different functional demands for the dissorophoids found at the Oklahoma locality.
Description[]
American paleontologist Samuel Wendell Williston used the details of the species Cacops aspidephorus to first describe its features. However, because of the poor preservation of specimens collected from the Cacops Bone Bed in Texas, other researchers who collected specimens from other localities have described many of Cacops’ features with more certainty.
Skull[]
The skull is very box-like and its cheeks aligned almost at a right angle to the skull table. The external cranial ornament is noticeable on the skull table and on top of the ridges that border the numerous depressions. One significant ontogenetic change in Cacops is a more evenly distributed ornamentation in the adults. Another important feature of the skull is the tip of the snout, which has a teardrop shaped internarial fontanelle, evident in both adult and juvenile specimens. Like other dissorophids, the temporal region of Cacops’ skull was dominated by the tympanic embayment, which likely housed a large tympanum. Marginal teeth are recurved and thinner than in other temnospondyls. The palatal dentition consists both of recurved tusks larger than the marginal teeth and strong recurved teeth that cover most of the palatal surface.
Vertebra and Osteoderms[]
Cacops was about 40 cm long. There is a change in shape and height of the presacral neural spine as you proceed posteriorly along the vertebral column. There are two sacral vertebrae and the pleurocentrum of the first sacral vertebrae is noticeably smaller that the rest. All internal osteoderms are fused to the neural spines. The osteoderms are associated with only the first 15 vertebrae, beginning at the axis. The lateral margin of each osteoderm can either be bluntly pointed or rounded. The osteoderms also have dermal pitting, each varying in size and depth. The distributions of these pits are not random, but rather found along the raised edges of the midsagittal groove and often in the groove as well. The ventral surface of both series of osteoderms does not have either grooves or pitting.
Paleobiology[]
Gallery[]
References[]
- Colbert, E. H., (1969), Evolution of the Vertebrates, John Wiley & Sons Inc (2nd ed.)
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