Clayton E. Ray

Bone histology of the ribs of the archaeocetes (Mammalia: Cetacea)

ABSTRACT Histological study of the ribs in two archaeocetes, Basilosaurus cetoides and Zygorhiza kochii, reveals conspicuous pachyostosis, with hyperostosis of periosteal cortices and absence of a free medullary cavity. In addition, abundant remains of calcified cartilage matrix, associated with extensive globular ossification, exist within the medulla. Among Cetacea, these features seem to be unique to the archaeocetes. Conversely, the structural peculiarities of bone in these animals are identical to those of the Sirenia and would arise from similar causes: inhibition of the chondroclastic and endosteal osteoclastic resorptions, and prolongation of subperiosteal osteogenesis during ontogeny, exemplifying morphological adaptation to aquatic life via heterochrony. The possible hormonal mechanisms of these features, as also their supposed adaptive consequences for the buoyancy of the archaeocetes, are discussed in relation to data already available for the Sirenia.

Skeleton of the Oldest Known Pinniped, Enaliarctos mealsi.

A nearly complete skeleton of the archaic pinniped Enaliarctos, found in late Oligocene or early Miocene rocks (approximately 23 million years old) of California, provides new evidence on the origin of pinnipeds. Enaliarctos retains many primitive features expected in the hypothesized common ancestor of pinnipeds. Skeletal modifications seen in Enaliarctos document swimming adaptations and indicate that pinnipeds primitively used the axial skeleton and both fore and hindflippers as sources of propulsion. Elongate hindlimbs with prominent bony processes (reflecting powerful musculature) suggest that Enaliarctos was more active on land than modern pinnipeds.

Skeletal morphology and locomotor capabilities of the archaic pinniped Enaliarctos mealsi

ABSTRACT A virtually complete skeleton of the pinniped Enaliarctos mealsi is described from the Pyramid Hill Sandstone Member of the Jewett Sand (late Oligocene or early Miocene) in central California. Skeletal evidence supports the sister group relationship of ursids and pinnipeds and the monophyly of pinnipeds. The structure of the vertebral column, especially the long transverse processes on the lumbar vertebrae and loose-fitting zygapophyses, indicates that the spine was capable of considerable flexion and extension. The limbs, modified as flippers with strongly developed bony processes and expanded areas for muscle attachment, provide evidence of their use in both aquatic and terrestrial locomotion.

Three Mammals New to the Pleistocene Fauna of Florida, and a Reconsideration of Five Earlier Records

Mormoops megalophylla (Peters), Conepatus leuconotus (Lichtenstein) and Felis pardalis Linn. are reported from Pleistocene deposits in Florida. Molossides floridanus G. M. Allen is transferred to the genus Eumops . The material upon which the reports of Erethizon dorsatum (Linn.), Mammuthus primigenius (Blumenbach) and Cervus canadensis Erxleben are founded is not adequate to justify inclusion of these species in the Pleistocene fauna of Florida. The record of Ovibovinae in the Pleistocene fauna of Florida is spurious.

Pre-Columbian Horses from Yucatan

The remains of horses have been reported from cave deposits in the state of Yucatan, Mexico, on two previous occasions. Mercer (the hill caves of yucatan, Lippincott, Phila., 1896, p. 172 and map opposite tide page) found horse remains in three caves in the Serrania, a low range of limestone hills lying in southwestern Yucatan and trending roughly parallel to the southwestern border of that state. The horse material was associated with pot sherds and other artifacts and showed no evidence of fossilization. Cope (in Mercer, op. cit. , p. 172, footnote) examined the material and …