. Bulletin. Natural history; Natuurlijke historie. COROSAURUS ALCOVENSIS 105. Fig. 52. Possible hypichnial groove casts of invertebrate horizontal feeding trails from Alcova Lime- stone, Milne Ranch, Muddy Mountain, Natrona County. Scale in centimeters. FOSSIL ASSEMBLAGE Few fossils are known from the Alcova Limestone. They occur sporadically, are generally poorly preserved, and have been only questionably identified. Few taxa are represented in the Alcova biota, which has generally been regarded as marine, but lacks the unequivocal occurrence of a marine organism. Vertebrate Fauna The most co
. Bulletin. Natural history; Natuurlijke historie. COROSAURUS ALCOVENSIS 105. Fig. 52. Possible hypichnial groove casts of invertebrate horizontal feeding trails from Alcova Lime- stone, Milne Ranch, Muddy Mountain, Natrona County. Scale in centimeters. FOSSIL ASSEMBLAGE Few fossils are known from the Alcova Limestone. They occur sporadically, are generally poorly preserved, and have been only questionably identified. Few taxa are represented in the Alcova biota, which has generally been regarded as marine, but lacks the unequivocal occurrence of a marine organism. Vertebrate Fauna The most conspicuous component of the Alcova fauna is the 'nothosaur' Corosaurus alcovensis, remains of which, while not extremely abundant, are not rare. It is assumed that this animal was an inhabitant of the Alcova basin and not a chance import, for it is a distinct genus and species uniquely known from the Alcova Limestone, and is unassociated with typical open marine faunas. If an occasional immigrant, obvious and well-known marine forms would be expected as well. Skeletal material of Corosaurus is so far restricted to the Casper-Muddy Mountain area of Natrona County, the section of maximum unit thickness. This may, however, be a function of the greater amount of rock exposed in this area. If a natural restriction, Corosaurus perhaps preferentially inhabited the relatively open waters of the central basin. As many of the bones have come from talus debris, the precise stratigraphic horizon from which they originated within the member is unknown. They were perhaps randomly distributed, although few specimens have been discovered in association with stromatolites. On the other hand, all Field Museum specimens were collected in situ from the upper half of the local profile. Most Corosaurus fossils consist of scattered or isolated elements; others are only partially articulated skeletons, sections of vertebral columns, or accumulations of gastralia. This disposition of fossils might sugge
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