Browsing by Author "Eldredge, Niles."
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Item The allopatric model and phylogeny in Paleozoic invertebrates—final draft.(1970a) Eldredge, Niles.1970 typescript of a manuscript published in 1971 in Evolution.Item April 1968 - Some Aspects of Species-Level Evolution in Paleontology(1968-04) Eldredge, Niles.Item Calmoniid trilobites of the Lower Devonian Scaphiocoelia zone of Bolivia, with remarks on related species. Bulletin of the AMNH ; v. 165, article 2(New York : American Museum of Natural History, 1980) Eldredge, Niles.; Branisa, Leonardo."The calmoniid trilobites of the Scaphiocoelia assemblage zone (Lower Devonian) of Bolivia are described. The Scaphiocoelia Zone is the oldest Devonian unit in Bolivia and is recognized in the base of the Belén Formation, the Icla Formation, and the Gamoneda Formation, in northern, central, and southern Bolivia, respectively. Twenty-one trilobite and one eurypterid taxa are recognized from this zone, 17 of which are species of Calmoniidae. Scaphiocoelia Zone calmoniids herein described as new include one genus (Deltacephalaspis), and five subgenera (Bainella (Belenops), the nominate subgenus of Deltacephalaspis, Deltacephalaspis (Prestalia), Schizostylus (Curuyella), and Kozlowskiaspis (Romanops)). Ten new Scaphiocoelia Zone species are described: D. (Deltacephalaspis) comis, D. (D.) retrospina, D. (D.) magister, D. (Prestalia) tumida, Schizostylus (Curuyella) granulata, ?Acastoides gamonedensis, Phacopina convexa, Kozlowskiaspis (Romanops) borealis, K. (Romanops) australis, and Tarijactinoides tikanensis. Additionally, two new species are characterized but not formally diagnosed, and two others are distinguished but remain unassigned to genera. Three previously described species from the Scaphiocoelia Zone are redescribed: Bainella (Belenops) insolita (Wolfart), Parabouleia calmonensis Eldredge, and Tarijactinoides jarcasensis Suárez Soruco. The vicariant pattern within Bolivia, and the biogeographic affinities of Bolivia with other areas within the Malvino-Kaffric Province are briefly discussed. We also present a general discussion of calmoniid anatomy and taxic diversity. Non-Scaphiocoelia Zone trilobites from Bolivia and elsewhere are also described, discussed or figured as a consequence of our study of the Scaphiocoelia Zone material. We describe the new genus Andinacaste from the Silurian of Bolivia. We describe as new Andinacaste legrandi and Phacopina padilla, the latter from the Icla Formation, above the Scaphiocoelia Zone, at Padilla, Bolivia. We present formal revisions for the following six genera: Bainella, Schizostylus, Phacopina, Kozlowskiaspis, Parabouleia, and Tarijactinoides. We discuss the status of three additional genera: Probolops, Acastoides, and Scotiella. We formally revise Kozlowskiaspis (Kozlowskiaspis) superna and Andinacaste chojnacotensis. Finally, we also discuss or figure an additional 15 calmoniid and acastid species in conjunction with our analysis of the composition of the calmoniid component of the Scaphiocoelia Zone fauna"--P. 185.Item February 1965 - Macroevolution Seminar.(1965-02) Eldredge, Niles.Item Figure 10 - Illustration.(1971) Eldredge, Niles.Three-dimensional sketch contrasting a pattern of relative stability (A) with a trend (B), where speciation (dashed lines) is occurring in both major lineages. Morphological change is depicted here along the horizontal axes, while the vertical axis is time. Though a retrospective pattern of directional selection might be fitted as a straight line in (B), the actual pattern is stasis within species, and differential success of species exhibiting morphological change in a particular direction.Item Gastropoda and Monoplacophora of the Solsville member (Middle Devonian, Marcellus Formation) in the Chenango Valley, New York State. Bulletin of the AMNH ; v. 144, article 2(New York : [American Museum of Natural History], 1971) Rollins, Harold B., 1939-; Eldredge, Niles.; Spiller, Judith.Item Letter from Eldredge to Dr. Thomas J.M. Schopf, June 21, 1971.(1971) Eldredge, Niles.Letter regarding Final version of manuscript, Eldredge and Gould, 1972.Item Observations on burrowing behavior in Limulus polyphemus (Chelicerata, Merostomata), with implications on the functional anatomy of trilobites. American Museum novitates ; no. 2436(New York, N.Y. : American Museum of Natural History, 1970) Eldredge, Niles."The functional morphology of burrowing was investigated in Limulus polyphemus with particular attention paid to the role played by the dorsal setae and prosomal shape. The burial process can be broken down into four discrete stages. Stage 1 involves active burial by downward flexion of the prosoma and a promotor-remotor swing (normal walking) by the prosomal legs. Sand is forced over the prosoma and anterior one-third of the opisthosoma, and a channel between these two structures is kept clear. Stage 2 involves no further burial, but rather active intake of water through one or both channels, deflection of the current back toward the gills underneath the opisthosoma, and expulsion of the current under one or both posterior opisthosomal projections. Stage 3 is the final burial phase and is effected both by forward walking and forceful flapping of the opisthosoma into the substratum; burial ceases when the last posterior opisthosomal projection is finally buried. The telson is covered throughout this process. Stage 4 is a long period of dormancy. The dorsal setae, distributed on the margins of the carapace, are mechanoreceptors that aid in keeping the organism buried. Their action is integrated with all other anatomical and behavioral aspects of burrowing, so that burrowing cannot be entirely disrupted by suppression of the tactile setae. Prosomal shape is at least partially explicable in terms of burrowing efficiency. The frontal arch is a necessary concomitant to a mode of burrowing that utilizes only normal promotor-remotor (walking) activity of the appendages; the arch effectively presents a horizontal edge to the substratum upon flexure of the prosoma of approximately 15 degrees. The high angle of slope of the margin of the carapace creates a thick wall of sediment that covers the rest of the body and allows burial within a minimum amount of space. The coaxial exite of the sixth prosomal appendage is a curved structure that probably deflects the current of water entering at the channel back toward the opisthosomal gill appendages, although they do not carry out this function alone. It may or may not be used to clean the gills, which is the function usually attributed to it. Limulus polyphemus possesses many anatomical similarities with trilobites. Detailed knowledge of the functional morphology of L. polyphemus may, if carefully applied, serve as a model for interpretation of trilobite morphology hitherto incompletely understood. In particular, the nature and role of the sensory dorsal setae and the functional aspects of the anterior arch in L. polyphemus appear to have a direct bearing on the interpretation of closely comparable structures in certain trilobites"--P. 16-17.Item Patterns and processes of stasis in two species lineages of brachiopods from the Middle Devonian of New York State. American Museum novitates ; no. 3114(New York, N.Y. : American Museum of Natural History, 1994) Lieberman, Bruce S.; Brett, Carlton E. (Carlton Elliot); Eldredge, Niles.Item The Process of speciation and interpretation of the fossil record.(1970) Eldredge, Niles.First draft of Eldredge and Gould, 1972.Item Revision of the pseudoniscine merostome genus Cyamocephalus Currie. American Museum novitates ; no. 2557(New York, N.Y. : American Museum of Natural History, 1974) Eldredge, Niles.; Plotnick, Roy E."We present an emended diagnosis for the monotypic genus Cyamocephalus Currie, 1927, based on examination of the holotype of Cyamocephalus loganensis and study of a second, very well-preserved specimen we attribute to Cyamocephalus cf. C. loganensis. Both specimens, which were collected from Upper Silurian rocks of Great Britain, are described in detail. The holotype specimen is remarkable in that a pair of dark stains, the possible remains of a portion of the dorsal longitudinal muscle system, are preserved within the cardiac lobe of the prosoma and the axial lobe of the opisthosoma. The prosomal morphology of Cyamocephalus is similar to that of other pseudoniscids; as in other Pseudoniscidae, cardiophthalmic morphology is obscure but similar in general plan to that of other Limulina. There are 10 opisthosomal segments; the first (anterior) segment is greatly reduced with very short pleura. Segments 2-10 have well-developed pleura, and segments 6 and 7 are fused into a solid tergite on which is developed a complex pattern of ridges and furrows. All other segments are freely articulated. The axial furrow system of segments 2-5 on the second specimen is also complex. The telson is styliform. Although clearly pseudoniscine in character, the large overall size, the proportionally large size and rounded posterior outline of the opisthosoma, and the complexities of the furrows of the axis and on segments 6 and 7, readily differentiate this genus from Pseudoniscus and other related genera. Recently regarded as incertae sedis within the Merostomata (Eldredge, 1974), we now consider Cyamocephalus a valid genus, in some respects the most specialized (derived) member of the family Pseudoniscidae (sensu Eldredge, 1974)"--P. 3.Item Revision of the suborder Synziphosurina (Chelicerata, Merostomata) : with remarks on merostome phylogeny. American Museum novitates ; no. 2543(New York, N.Y. : American Museum of Natural History, 1974) Eldredge, Niles.; Smith, LeGrand."A new genus and species of the merostome suborder Synziphosurina is described from the Lower Devonian of Bolivia. This new taxon has made possible a reinterpretaion of other poorly understood genera commonly allocated to the Synziphosurina. Weinbergina Richter and Richter, Bunodes Eichwald, Bunaia Clarke, and Pseudoniscus Niezkowski are re-examined in detail, based mainly on a study of the original material, as well as on collections of topotypical specimens of Bunodes lunula Eichwald and Pseudoniscus aculeatus Niezkowski. Shorter discussions are presented for Neolimulus Woodward and Limuloides Salter in Woodward. Weinbergina and the new Bolivian genus are monotypic. Each is known from only three specimens, and both occur in Lower Devonian marine rocks. Bunodes as presently understood is also monotypic: B. lunula from the Upper Silurian of Oesel; some British Silurian species described as Limuloides are probably referable to Bunodes. The three described species of Pseudoniscus (P. aculeatus Niezkowski from Oesel; P. roosevelti Clarke, and P. clarkei Ruedemann from New York State), all Upper Silurian in age, are difficult to differentiate, and only the genus is rediagnosed. In addition, two specimens of Pseudoniscus are now known from the Silurian of Great Britain. Neolimulus, based on a single specimen from the Upper Silurian of England, is poorly known and apparently closely related to Pseudoniscus. Bunaia is based on four specimens (from the Upper Silurian of New York) and may be a junior synonym of Pseudoniscus. The suborder Synziphosurina is rediagnosed and contains but four valid genera: Weinbergina, Bunodes, Limuloides, and the new Bolivian taxon. The families Weinberginidae (Weinbergina and the Bolivian genus) and Bunodidae (Bunodes and Limuloides) are recognized. The suborder Limulina is the sister group of the Synziphosurina, and in turn is comprised of the infraorders Pseudoniscina (diagnosed herein) and Limulicina. Pseudoniscus, Bunaia, and Neolimulus are referred to the Pseudoniscina, as is an unnamed family of primitive belinurid limulines in which the axis of the opisthosoma is broader than the prosomal cardiac lobe at the juncture of these two tagmata. A classification of the class Merostomata is presented: the Aglaspida comprise the sister group of the Xiphosurida (i.e., Synziphosurina and Limulina) and the Eurypteridida and Chasmataspida are probably sister taxa. Two merostome subclasses, the Eurypterida and Xiphosura, are recognized. Finally, there is a brief discussion of evolutionary patterns within the Merostomata, with emphasis on the Xiphosurida"--P. 3.Item Speciation and Punctuated Equilibria: An Alternative to Phyletic Gradualism. [2nd draft](1972) Eldredge, Niles.Second draft of Eldredge and Gould, 1972Item Speciation and Punctuated Equilibria: An Alternative to Phyletic Gradualism. [3rd draft](1972) Eldredge, Niles.; Gould, Stephen Jay.Third draft of Eldredge and Gould, 1972.Item Systematics and evolution of Phacops rana (Green, 1832) and Phacops iowensis Delo, 1935 (Trilobita) from the Middle Devonian of North America. Bulletin of the AMNH ; v. 147, article 2(New York : [American Museum of Natural History], 1972) Eldredge, Niles."Two trilobite species, Phacops rana (Green, 1832) and Phacops iowensis Delo, 1935, from the Middle devonian of North America, are analyzed in detail from the point of view of geographic and stratigraphic variation. A purely morphological, as opposed to biostratigraphic, approach is used in analyzing relationships among subtaxa of the two species. Subsequent comparison of the relative sequence of inferred evolutionary events with documented biostratigraphic distributions allows an analysis of trends (biostratigraphic character gradients), character displacement between the two species, and mode of origin of the subtaxa. The schizochroal eye of these species is the most important anatomical complex in terms of both intrapopulational and interpopulational variation and species discrimination. Lens number per eye may be broken down into number of dorsoventral files (vertical columns of lenses) and number of lenses per dorsoventral file. The adult population number of dorsoventral files per eye in Phacops is reached early in ontogeny and is stabilized; the number of dorsoventral files is the most consistently reliable criterion for discrimination of the two species. Throughout its history, P. iowensis had 13 dorsoventral files in normal adults. This species belongs to a native North American phacopid lineage that can be traced back at least as far as the Gedinnian ('Phacops' logani Hall). Phacops rana, morphologically closest to P. schlotheimi (Bronn) from Europe and elsewhere, has from 15 to 18 dorsoventral files. Most of the history of species involved the reduction from 18 to 15 files; the reduction is an allopatric phenomenon, involving transitional populations acquiring a reduced number of dorsoventral files on the eastern margin of the craton (exogeosyncline), which subsequently invade the cratonal interior. Other evolutionary changes in the P. rana lineage appear to be phyletic trends. The two species are nearly mutually exclusive, though coeval and their geographic ranges overlap considerably. Although P. iowensis occurs from Iowa to New York, it was confined to the Michigan Basin for the larger part of its history. Phacops rana is found from New York south to Virginia and west as far as Iowa. Phacops iowensis was by far the more stable through time; it is invariably rare, and generally confined to purer limestones. The one case of sympatry between rana and iowensis occurs in the Hungry Hollow Formation of Ontario, resulting in morphological changes in the two species which are best explained as character displacement. The P. rana lineage as a whole converged on iowensis in number of dorsoventral files and in many ornamental features; the convergence was closest in the Taghanic. The distribution of, and interactions between, Phacops rana and Phacops iowensis are best explained as if the two taxa are considered true 'bio-species.' Although the little change that occurred within the iowensis lineage seems to have been phyletic in nature, the allopatric model is necessary to account for the more important evolutionary changes in P. rana. Five subspecies of Phacops rana, including P. rana paucituberculata, new subspecies, and three subspecies of P. iowensis, are recognized"--P. 49.Item Systematics of Lower and Lower Middle Devonian species of the trilobite Phacops Emmrich in North America. Bulletin of the AMNH ; v. 151, article 4(New York : [American Museum of Natural History], 1973) Eldredge, Niles."Six species (one new) including 20 subspecies (4 new) of Phacops are recognized from the Lower and Middle Devonian of North America. Gedinnian-Siegenian species include P. logani Hall, 1861, and P. claviger Haas, 1969. Phacops clarksoni, new species, occurs in the Emsian Schoharie Formation of New York, and P. cristata Hall, 1861, occurs in the Emsian and Eifelian of the Appalachian Province. Phacops iowensis Delo, 1935, and P. rana (Green, 1832) occur in Givetian strata. A conservative position is taken on generic nomenclature and defended herein; all species, with the exception of P. rana are closely related and belong to the same monophyletic taxon. Special topics include a quantitative analysis of eye polymorphism and ontogeny in Phacops logani birdsongensis Delo, 1940, and P. logani raymondi (Delo, 1935), and of eye ontogeny in Phacops cristata stummi, new subspecies and P. c. canadensis (Stumm, 1954). Cladistic methodology in paleontology is briefly discussed, and theories of relationship among all subspecies and species are presented. A key to all Devonian phacopid taxa considered valid herein is included"--P. 289.