Browsing by Author "Boyd, Donald Wilkin."
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Item Hinge grades in the evolution of crassatellacean bivalves as revealed by Permian genera. American Museum novitates ; no. 2328(New York, N.Y. : American Museum of Natural History, 1968) Boyd, Donald Wilkin.; Newell, Norman Dennis, 1909-"The origin and affiliation of the conservative bivalve superfamily Crassatellacea Férussac, 1882 (= Astartacea d'Orbigny, 1844), have been uncertain. Some authors have regarded these mollusks as lucinoids. Others have placed them with the cyrenoids, or in a separate order of the Heterodonta, the 'Astartedonta.' Our discovery of numerous exceptionally well-preserved examples of the Crassatellacea of Permian age in Wyoming clarifies some problems of the early history of the group, showing how, by the acquisition of additional hinge teeth after Permian time, the hinge of living crassatellaceans became modified in separate lines from basically lucinoid to a more advanced hinge grade. Representatives of post-Paleozoic Crassatellidae and Astartidae through convergent evolution resemble one another more closely than do their Paleozoic ancestors, the new subfamilies Oriocrassatellinae and Astartellinae. Members of these Paleozoic subfamilies are sufficiently dissimilar to suggest a diphyletic origin for the Crassatellacea. The Bernard and Munier-Chalmas hinge formula and its implication of dental homologies are discussed, and a simplified, more objective hinge notation based on the Steinmann system is employed. Two new species, Oriocrassatella elongata and Astartella aueri, are described. Examples of hinge transposition of cardinal and anterior lateral teeth, but not the posterior laterals, are recorded in both. This partial transposition of hinge teeth, recorded for the first time in Paleozoic bivalves, indicates that the posterior laterals are genetically independent of the other hinge teeth"--P. [1]-2.Item Iteration of ligament structures in pteriomorphian bivalves. American Museum novitates ; no. 2875(New York, N.Y. : American Museum of Natural History, 1987) Newell, Norman Dennis, 1909-; Boyd, Donald Wilkin."Pteriomorphia, the largest subclass of the Bivalvia, includes such highly successful extant groups as the marine mussels, pearl shells, oysters, and scallops. Shells of different groups display surprisingly diverse structural types of ligaments (diagnostic traces of which are recognizable in fossils as old as the early Cambrian) and the ligaments have figured prominently in pteriomorph classifications. Within the context of general morphology, seven or eight ligament grades have been used to characterize families of pteriomorphs. But the same, or very similar, ligaments appear repeatedly as evolutionary novelties in separate taxonomic groups without evident phyletic origins or marked adaptive significance. Even their phylogenetic polarity is frequently in doubt. For example, one complex structure (duplivincular) is replaced geochronologically by a different, and simpler structure (alivincular) in families of the Arcacea, Anomiacea, Aviculopectinacea, and Pteriacea. 'Transitional' (new term), multivincular, and duplivincular ligaments all occur in the superfamily Pteriacea. Even where the geological succession of ligaments might be interpreted as indicating an ancestral-descendant relationship, the different grades of ligaments do not form gradational morphoclines. So this review is intended only to call attention to taxonomic and phylogenetic difficulties in evaluating ligament grades; we are withholding conclusions about classification until later"--P. [1].Item Nacre in a Carboniferous pectinoid mollusc and a new subfamily Limipectininae. American Museum novitates ; ; no. 2970.(New York, N.Y. : American Museum of Natural History, 1990) Newell, Norman Dennis, 1909-; Boyd, Donald Wilkin.Item A new Lower Triassic Permophorus from the central Rocky Mountains. American Museum novitates ; no. 3263(New York, NY : American Museum of Natural History, 1999) Newell, Norman Dennis, 1909-; Boyd, Donald Wilkin.Item Notes on micro-fabric in Upper Paleozoic scallops. American Museum novitates ; no. 2816(New York, N.Y. : American Museum of Natural History, 1985) Newell, Norman Dennis, 1909-; Boyd, Donald Wilkin."Microstructure of the outer shell layer of Upper Paleozoic pectinoid bivalves usually, but not always, is strikingly different in right and left valves, and the differences characterize groups at the generic and familial levels, serving to augment sparse morphologic characters available for taxonomic and phylogenetic studies. The progress note given here is one aspect of an ongoing comprehensive taxonomic survey of Permian and Lower Triassic Pectinacea"--P. [1].Item Oyster-like Permian Bivalvia / Norman D. Newell, Donald W. Boyd. Bulletin of the AMNH ; v. 143, article 4(New York : [American Museum of Natural History], 1970) Newell, Norman Dennis, 1909-; Boyd, Donald Wilkin.Item Parallel evolution in early trigoniacean bivalves. Bulletin of the AMNH ; v. 154, article 2(New York : American Museum of Natural History, 1975) Newell, Norman Dennis, 1909-; Boyd, Donald Wilkin."The present work is a morphologic-taxonomic revision and inquiry into the evolution of geologically ancient (late Paleozoic and Triassic) marine bivalves of a formerly cosmopolitan superfamily Trigoniacea that are represented today by a single Australian genus Neotrigonia. Trigoniaceans, after a very long period of extreme conservatism, underwent a notable radiation in the Jurassic and Cretaceous periods, then nearly became extinct immediately afterward. Particular attention is devoted here to stratigraphic-morphologic analysis from which it is concluded that the complex hinge of the younger genera probably is of diverse origin as apparently it was attained after divergence of separate lines. Each line is characterized by chronological propinquity of relatively stable surface markings and external form. The modified taxonomic arrangement adopted here recognizes the polyphyletic attainment of the derived hinge characters shared in common by the most advanced genera of trigoniaceans. It results in improved resolution of phylogenetic and biostratigraphic problems as contrasted with the more generalized conventional 'horizontal' scheme of classification. Much of the memoir reports our original observations on morphologic details and anatomy of living and fossil trigoniaceans from Australia, Europe, and America and attempts a taxonomic revision of 27 North American Upper Carboniferous and Permian species. New families introduced here are the: Eoschizodidae, Eoastartidae, and Costatoriidae. The following genera are given more than perfunctory attention: Devonian only: Eoschizodus, Rhenania, Hefteria; Devonian to Permian: Schizodus; Permian only: Heteroschizodus, new genus, Lyroschizodus, new genus, Procostatoria, new genus, Paraschizodus, new genus, Scaphellina, Eoastarte, and Kaibabella; both Permian and Triassic: Neoschizodus and Costatoria; Triassic only: Heminajas, Pachycardia, Trigonodus, Gruenewaldia, Lyriomyophoria, and Costatoria"--P. 57.Item Pectinoid bivalves of the Permian-Triassic crisis. Bulletin of the AMNH ; no. 227([New York] : American Museum of Natural History, 1995) Newell, Norman Dennis, 1909-; Boyd, Donald Wilkin."This contribution concludes a general revision of genera of pectiniform bivalves (pectinoids) of the world's marine rocks near the Permo-Triassic boundary. The study includes the morphology, taxonomy, and distribution of some 20 families and 30 genera, several of them new (for new taxa see Contents). It is based on the best material available anywhere, mainly from the western United States. The known diversity of these early pectinoids declined gradually from about 23 genera in the Guadalupian (M. Permian) to a minimum of 5 in the Griesbachian (L. Triassic). After the biological decline, they did not recover substantial diversity until late Triassic (Norian) time. So they shared the great mass extinction with most other groups of marine invertebrates. The crisis extended over some tens of millions of years and was slow, rather than catastrophic. This diversity pattern agrees well with carbon isotope ratios that seem to reflect a depressed oceanic productivity in early Triassic time"--P. 5.Item Permian pelecypods from Tunisia. American Museum novitates ; no. 2686(New York, N.Y. : American Museum of Natural History, 1979) Boyd, Donald Wilkin.; Newell, Norman Dennis, 1909-"Fifteen late Permian pelecypod species belonging to 15 genera and 13 families are described from Tunisia. Shikamaia ? ogulineci, a remarkable ambonychiacean, Gigantocyclus zidensis, a lucinid of surprisingly modern aspect, and a new species, Lyroschizodus djemelensis are morphologically unusual elements of the fauna. A new non-byssate pterinopectinid, Denguiria azzouzi, new genus and new species, is described. A minor element of an extraordinarily rich assemblage of marine invertebrates dominated by reef-building calcareous sponges, the pelecypods show surprisingly little resemblance to contemporaneous assemblages of other areas"--p. [1].Item Permian scallops of the pectinacean family Streblochondriidae. American Museum novitates ; no. 2831(New York, N.Y. : American Museum of Natural History, 1985) Newell, Norman Dennis, 1909-; Boyd, Donald Wilkin."Permian scallops of the genera Streblochondria and Guizhoupecten, family Streblochondriidae, are here revised with the aid of superb collections of silicified specimens from western Texas. The more specialized of the two genera, Guizhoupecten, shares several 'derived' characters with the post-Paleozoic family Pectinidae. This study illustrates the necessity of large, well-preserved collections for evaluating variable populations. Phylogenetic and ecological conclusions are deferred until we can properly document associated taxa"--P. [1].Item Phylogenetic implications of shell microstructure in the Pseudomonotidae, extinct Bivalvia. American Museum novitates ; ; no. 2933.(New York, N.Y. : American Museum of Natural History, 1989) Newell, Norman Dennis, 1909-; Boyd, Donald Wilkin.Item A reappraisal of trigoniacean families (Bivalvia) and a description of two early Triassic species. American Museum novitates ; no. 3216(New York, N.Y. : American Museum of Natural History, 1997) Boyd, Donald Wilkin.; Newell, Norman Dennis, 1909-Item Silicified Leptodesma (Bivalvia; Pteriomorphia) from the Texas Permian. American Museum novitates ; no. 3347(New York, NY : American Museum of Natural History, 2001) Boyd, Donald Wilkin.; Newell, Norman Dennis, 1909-; Cooper, G. Arthur (Gustav Arthur), 1902-; National Museum of Natural History (U.S.)The description here of Leptodesma falcata, new species, continues our ongoing study of bivalve mollusks of the Permian-Triassic faunal crisis. Our collection of silicified valves is from a single locality in the intensively sampled Permian strata of West Texas, which suggests that L. falcata appeared and became extinct rapidly. Such easily missed endemic populations may explain the disjunct records of some Permo-Triassic Lazarus taxa. Unusual features of the new species include its simple dentition, in contrast to the complex array of teeth of middle Paleozoic pterineids, and its evidence of fibrous prismatic microstructure, an addition to the known microstructural variability of the family.Item A unique pterioid bivalve from the early Triassic of Utah. American Museum novitates ; no. 3375(New York, NY : American Museum of Natural History, 2002) Boyd, Donald Wilkin.; Newell, Norman Dennis, 1909-The new species Bakevellia? silberlingi is described from a single locality in the upper Thaynes Formation (mid-Spathian) near Salt Lake City. The 133 specimens studied are natural casts of siltstone freed from limestone in the laboratory by acid dissolution. In external form, B.? silberlingi resembles inequivalved and auriculate taxa of several pterioid families. However, its peculiar combination of hinge characters precludes unqualified assignment to either an established genus or family. The shallow, troughlike ligament scar extending backward from the beak resembles that of some pteriids, whereas the numerous teeth form a pattern typical of multivincular bakevelliids and their putative duplivincular ancestors. The new form is provisionally assigned to Bakevellia in recognition of the numerous characters it has in common with that familiar genus. The single-locality occurrence and unlikely mode of fossilization of this unusual taxon suggest that a significant amount of the diversity of early Triassic marine faunas may consist of short-lived, geographically isolated taxa awaiting discovery.