Browsing by Author "Schaeffer, Bobb, 1913-"
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ItemAnurans from the early Tertiary of Patagonia. Bulletin of the AMNH ; v. 93, article 2(New York : [American Museum of Natural History], 1949) Schaeffer, Bobb, 1913-; Simpson, George Gaylord, 1902-; Scarritt Patagonian Expedition 1930-1931); Scarritt Patagonian Expedition 1933-1934) ItemThe braincase of the holostean fish Macrepistius, with comments on neurocranial ossification in the Actinopterygii. American Museum novitates ; no. 2459(New York, N.Y. : American Museum of Natural History, 1971) Schaeffer, Bobb, 1913-; Scott, Gayle, 1894-"The braincase of Macrepistius arenatus from the Glen Rose Formation (Lower Cretaceous, Albian) of Texas resembles that of other caturids in the following ways: (1) It has a completely ossified interorbital septum and otic region; (2) It possesses both autopterotic ("opisthotic") and prootic ossifications; and (3) It has an enlarged intercalar that partly surrounds the vagal foramen. It differs from other caturids (and apparently from other actinopterygians) in having paired, partly fused, supraoccipitals that are clearly separated from the epiotics. The parasphenoid is toothless and lacks basipterygoid processes. The cranial wall is complete in the area of the trigeminofacialis chamber. The jugular canal is represented by an opening medial to the ascending process of the parasphenoid. A recess below the jugular canal that has separate openings for the palatine and hyomandibular nerves probably contained the facial ganglion. The trigeminofacialis chamber is here defined as the extramural space between the lateral commissure and the primordial lateral wall of the braincase. This chamber has never been secondarily divided into a pars ganglionaris and a pars jugularis in the actinopterygians (as originally claimed by Allis, 1919) although its boundaries and associated foramina have been modified in various ways. An attempt to work out the relationships of Macrepistius on the basis of shared derived characters has resulted in two hypotheses--a 'sister' relationship with either Osteorhachis or Heterolepidotus. Because of insufficient evidence it is not possible to favor either hypothesis. The analysis of caturid and other amiiform character states indicates, however, that the unique specializations of Macrepistius evolved from a caturid with pointed teeth, relatively narrow palate and infraorbitals and no supraoccipitals. Comparison of the neurocranial ossification pattern in Macrepistius with that in a variety of other actinopterygians has emphasized the basic uniformity of the pattern throughout the holosteans, halecostomes, and teleosts, as noted by Rayner (1948). This situation presumably reflects the disposition of the embryonic ossification sites in the palaeonisciform neurocranium, which, in the adult, is usually composed of two major ossifications. The persistence of numerous separate neurocranial bones in the higher actinopterygian groups probably represents a neotenic adaptation of prolonged differential growth of the braincase beyond the chondrocranial stage. These conclusions are based, in part, on neurocranial ossification patterns in an immature specimen of the palaeonisciform Cosmoptychius and in adult specimens of Birgeria and Polypterus. Factors that determine the location and number of neurocranial ossification centers in relation to the chondrocranial model, the organization of the ossification centers in relation to the formation of a particular bone, and finally, the conditions that promote or inhibit perichondral and endochondral ossification in a particular part of the neurocranium (or in the rest of the endoskeleton) are poorly understood. In the absence of pertinent experimental data we can do little more than speculate on these problems. There is, however, circumstantial evidence that the extent of perichondral and endochondral ossification represents a compromise between the ancestral genotype and factors such as stress, buoyancy, equilibrium, and protection"--P. 30-31. ItemCoelacanth fishes from the continental Triassic of the western United States. American Museum novitates ; no. 2036(New York, N.Y. : American Museum of Natural History, 1961) Schaeffer, Bobb, 1913-; Gregory, Joseph Tracy, 1914-"There is now conclusive evidence that coelacanths are present in both the lower and the upper Triassic continental beds of the western United States. The scarcity of their remains is, in part, related to the factors that are responsible for the general rarity of fishes in these formations. The broad, flat, flood-plain environment in which the Moenkopi and Chinle-Dockum sediments were deposited (McKee, 1954; Stewart et al., 1959) was apparently more favorable for the preservation of terrestrial than of aquatic vertebrates. Metoposaur and phytosaur remains are much more abundant and more widely distributed than fish remains. The latter are restricted, as might be expected, to channel and lacustrine deposits. Although isolated actinopterygian scales are reasonably common in such deposits, associated fish remains are extremely rare. At a few localities in the Chinle complete fishes have been found in great abundance. These usually occur in lacustrine deposits in concentrations suggestive of periodic mass mortality. The apparent rarity of coelacanth remains in these concentrations suggests that they were not common in the lakes and ponds of the Chinle flood plain. On the other hand, there is no positive evidence that they were, in general, restricted to rivers and streams. Except for the Moenkopi occurrence, which is quite clearly fluviatile, the paleoecologic picture is unsettled. Isolated coelacanth bones from the Moenkopi formation include distinctive basisphenoids, the morphology of which provides the basis for establishing a new genus and species, Moenkopia wellesi. Specimens thus far recovered from the late Triassic Dockum and Chinle formations are too incomplete to permit generic identification"--P. 15-17. ItemCretaceous and Tertiary actinopterygian fishes from Brazil. Bulletin of the AMNH ; v. 89, article 1(New York : [American Museum of Natural History], 1947) Schaeffer, Bobb, 1913- ItemCretaceous fishes from Bolivia, with comments on pristid evolution. American Museum novitates ; no. 2159(New York, N.Y. : American Museum of Natural History, 1963) Schaeffer, Bobb, 1913- ItemThe Cretaceous holostean fish Macrepistius. American Museum novitates ; no. 2011(New York, N.Y. : American Museum of Natural History, 1960) Schaeffer, Bobb, 1913-; Cope, E. D. (Edward Drinker), 1840-1897.; Hill, Robert Thomas, 1858-1941. ItemAn early Triassic fish assemblage from British Columbia. Bulletin of the AMNH ; v. 156, article 5(New York : American Museum of Natural History, 1976) Schaeffer, Bobb, 1913-; Mangus, Marlyn.; Laudon, Lowell Robert, 1905-; American Museum of Natural History-National Museum of Canada Expedition (1961-1962)"A Lower Triassic (Sulphur Mountain Formation) marine fossil fish assemblage from the Wapiti Lake area, British Columbia, is described. It includes the following taxa: cf. Palaeobates, Chondrichthyes, incertae sedis, Pteronisculus sp., Birgeria sp., Boreosomus sp., Bobasatrania canadensis, cf. Perleidus, Australosomus sp., Saurichthys sp., Parasemionotidae, incertae sedis, Albertonia cupidinia, and Whiteia sp. Most of these forms, or close relatives, are also known from the marine Lower Triassic rocks of East Greenland, Spitzbergen, and Madagascar. Although the Wapiti Lake specimens have not added significantly to our knowledge of the morphology and systematics of marine Scythian fishes, the assemblage has helped us understand their paleozoogeographic distribution around the periphery of Pangaea"--P. 519. ItemAn Eocene serranid from Patagonia. American Museum novitates ; no. 1331(New York City : The American Museum of Natural History, 1947) Schaeffer, Bobb, 1913-; Simpson, George Gaylord, 1902-; Scarritt Patagonian Expedition 1930-1931) ItemA Jurassic fish from Antartica. American Museum novitates ; no. 2495(New York, N.Y. : American Museum of Natural History, 1972) Schaeffer, Bobb, 1913-; Elliot, David H."The first Mesozoic actinopterygian fishes from Antarctica were discovered in lacustrine interbeds within the Lower Jurassic Kirkpatrick Basalt, in the Transantarctic Mountains, Victoria Land. Except for an enigmatic patch of scales, all the specimens collected are assigned to a new genus and species, Oreochima ellioti, which is placed in the pholidophoriform family Archaeomaenidae. Prior to this discovery, the archaeomaenids were known only from Lower Jurassic continental deposits of Australia"--P. . ItemJurassic fishes from the western United States, with comments on Jurassic fish distribution. American Museum novitates ; no. 2796(New York, N.Y. : American Museum of Natural History, 1984) Schaeffer, Bobb, 1913-; Patterson, Colin."Seven genera of fishes from the Jurassic (Upper Bathonian-Callovian) Sundance and Wanakah formations of western United States are described and their relationships discussed together with a review of their stratigraphic occurrence. The assemblage includes isolated teeth of the chondrichthyans Hybodus sp. and Ischyodus sp., in part from unrecorded Sundance localities near Hulett, Wyoming. Most common is the generalized neopterygian Hulettia americans (Eastman), new genus of unknown relationship, which occurs in the Sundance of Montana and Wyoming, and in the Wanakah of Colorado (including the Pony Express Limestone) and New Mexico (Todilto Limestone). Lepidotes sp. and Caturus dartoni (Eastman), which belong to a monophyletic species group within the genus Caturus, are both present in the Sundance and the Wanakah. Occithrissops willsoni, new genus, new species from the Sundance, is an ichthyodectiform teleost, but not assignable to suborder. Todiltia schoewei (Dunkle), new genus from the Wanakah, is a teleost compared with Ascalabos and Leptolepis, but its affinities remain unknown. The problem of incertae sedis genera and species (e.g., the monotypic Hulettia) is discussed in regard to identification and relationships of Jurassic fishes from other parts of the world. Included tables and paleogeographic maps show temporal and spatial distribution of these fishes, but variable preservation, inadequate description, and superficial systematic analysis usually preclude detailed comparisons of Jurassic taxa from the literature. It is probable, however, that most Jurassic fish assemblages, like those of the Sundance-Wanakah, are mixtures of form genera and monotypic genera whose relationships are imprecisely known"--P. 2. ItemLate Triassic fishes from the western United States. Bulletin of the AMNH ; v. 135, article 6(New York : [American Museum of Natural History], 1967) Schaeffer, Bobb, 1913- ItemMalacostracan crustacean fauna from the Sundance Formation (Jurassic) of Wyoming. American Museum novitates ; no. 2652(New York, N.Y. : American Museum of Natural History, 1978) Herrick, Elizabeth M.; Schram, Frederick R., 1943-; Schaeffer, Bobb, 1913-"The only marine Jurassic decapod fauna in North America is found in the Stockade Beaver Member of the Sundance Formation of Wyoming. The preservation of these crustaceans is only moderately good, permitting, at most, identification to the generic level of these soft-shelled decapod shrimp. The faunal assemblage, composed of Antrimpos sp., Bombur sp., Mecochirus sp., a glypheid, and some unidentifiable anomuran remains, can be compared with Triassic and Jurassic material from European deposits, which form part of the biologic continuum of crustaceans throughout the Lower Mesozoic"--P. . ItemMendocinia, a subholostean fish from the Triassic of Argentina. American Museum novitates ; no. 1737(New York, N.Y. : American Museum of Natural History, 1955) Schaeffer, Bobb, 1913- ItemThe morphological and functional evolution of the tarsus in amphibians and reptiles. Bulletin of the AMNH ; v. 78, article 6.(New York : The American Museum of Natural History, 1941) Schaeffer, Bobb, 1913- ItemA new actinopterygian fish from the Cretaceous of North America. American Museum novitates ; no. 2344(New York, N.Y. : American Museum of Natural History, 1968) Schaeffer, Bobb, 1913- ItemNotes on the origin and function of the artiodactyl tarsus. American Museum novitates ; no. 1356(New York City : The American Museum of Natural History, 1947) Schaeffer, Bobb, 1913-"The definitive artiodactyl tarsus as it first appears in Lower Eocene deposits represents the abrupt introduction of a basic ordinal character. There are no known intermediate or transitional stages between this tarsus and the presumed ancestral type. Predator pressure must have been an important factor in the apparent rapid evolution of this structure, which had virtually reached the biomechanical limit of specialization by the Lower Eocene. 2. Available evidence indicates that the artiodactyls evolved from the primitive hyopsodontid condylarths, although the tarsus of these early ferungulates is very similar to that of the arctocyonid creodonts. In these types, the astragalus has a shallow tibial trochlea, a wide interarticular sulcus, and a rounded head. The calcaneum has a well-developed interosseous fossa and a robust sustentaculum supporting, in part, the astragalus. 3 The axes of the upper and lower ankle joints and the transverse tarsal joint have been determined for the arctocyonid creodont Claenodon. These axes are oriented in several different planes, suggesting the condition occurring in the tarsus of the chimpanzee and man, which may be close to the generalized eutherian arrangement. The probable motion at each of these joints is discussed. 4. The primitive artiodactyl tarsus differs markedly from the generalized ferungulate type. The astragalus has a deep tibial trochlea, the interarticular sulcus has disappeared in connection with a reorientation of the astragalocalcaneal and sustentacular facets, and the head is trochleated. The calcaneum has lost the interosseous fossa, and the sustentaculum no longer offers direct support to the astragalus. 5. The axes of the three ankle joints have been worked out for Ovis. With the changes in the astragalus and calcaneum noted above, these axes are now oriented in such a manner as to permit rotation of the astragalus in a vertical plane. This motion is demonstrated in a series of X-rays of the foot of a living goat. 6. The ligaments of the artiodactyl tarsus have been modified to permit vertical astragalar rotation. The fibers of the calcaneotibial and superficial calcaneal ligaments are somewhat spiraled in order to maintain effectively the integrity of the ankle joint during this rotation. 7. The transformation of the artiodactyl astragalus and calcaneum from the Claenodon type is described in detail by the use of the deformed coördinate method. The limitations of the method are discussed. 8. An attempt is made to describe the function of the artiodactyl tarsus, particularly in relation to astragalar rotation. The astragalus is essentially a cam-like structure that may be considered as a velocity mechanism. It also aids in increasing the angle of application of the crural flexor musculature at the start of the propulsive phase when two tarsal fulcra are probably present, at the upper ankle joint and the transverse tarsal joint"--P. 22-23. ItemOn the relationships of the Triassic-Liassic redfieldiiform fishes. American Museum novitates ; no. 2795(New York, N.Y. : American Museum of Natural History, 1984) Schaeffer, Bobb, 1913-"A survey of character distributions among the extinct lower actinopterygians has corroborated the hypothesis that the freshwater, Triassic-Liassic redfieldiiform fishes form a monophyletic group. This proposal is based mainly on the pattern of the dermal snout, loss of anterior nares, and presumably independent reduction of the branchiostegal series. The sister group of the redfieldiiforms among the other extinct lower actinopterygians remains unknown, but a survey of the dermal skull in these fishes has provided a hypothetical 'sister' pattern"--P. . ItemA palaeonisciform braincase from the Permian of Texas, with comments on cranial fissures and the posterior myodome. American Museum novitates ; no. 2658(New York, N.Y. : American Museum of Natural History, 1978) Schaeffer, Bobb, 1913-; Dalquest, Walter Woelber, 1917-"A single, large palaeonisciform braincase from the Lower Permian Lueders Formation, Baylor County, Texas, is described as a new genus and species within the Palaeonisciformes, incertae sedis. This specimen has also occasioned a review of the actinopterygian cranial fissures and the posterior myodome"--P. . ItemThe palaeoniscoid fish Turseodus from the Upper Triassic Newark group. American Museum novitates ; no. 1581(New York : American Museum of Natural History, 1952) Schaeffer, Bobb, 1913- ItemThe pes of Bauria cynops Broom. American Museum novitates ; no. 1103(New York City : The American Museum of Natural History, 1941) Schaeffer, Bobb, 1913-; Broom, Robert, 1866-1951.