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Tytuł:
A taxonomic and phylogenetic review of the anhanguerid pterosaur group Coloborhynchinae and the new clade Tropeognathinae
Autorzy:
Holgado, B.
Pegas, R.V.
Powiązania:
https://bibliotekanauki.pl/articles/2082272.pdf
Data publikacji:
2020
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Pterosauria
Pterodactyloidea
morphology
taxonomy
phylogeny
Cretaceous
USA
United Kingdom
Opis:
Anhanguerids are a particular group of pterodactyloid pterosaurs, characterized mainly by their rostral sagittal crests, well laterally expanded jaw tips and enlarged anterior teeth. Due to the fragmentary nature of most known specimens, including holotypes, the taxonomy of the group has proved particularly difficult and controversial. Coloborhynchinae is a recently proposed clade within the Anhangueridae, and was defined as the most inclusive clade containing Coloborhynchus clavirostris but not Anhanguera or Ludodactylus. Coloborhynchinae was originally thought to include Coloborhynchus, Uktenadactylus, and Siroccopteryx. Here we present a reassessment of the taxonomy and phylogeny of all proposed members of the Coloborhynchinae and Coloborhynchus complex, with new anatomical comparisons and a novel phylogenetic analysis. Several features allow us to establish that coloborhynchines were much more diverse than previously thought, englobing four genera and seven species: Aerodraco sedgwickii gen. et comb. nov., Coloborhynchus clavirostris, Nicorhynchus capito gen. et comb. nov., Nicorhynchus fluviferox gen. et comb. nov., Uktenadactylus rodriguesae sp. nov., and Uktenadactylus wadleighi. Nicorhynchus and Uktenadactylus are considered sister taxa, being distinct on the basis of several rostral characters. Although with a homoplastic flat rostrum surface, Siroccopteryx was recovered out of the Coloborhynchinae, as sister taxon of Tropeognathus, due to similarities on the palatal ridge (which is broad and deep, and starting at the same level) and the relatively stout teeth compared to other anhanguerids. Tropeognathus and Siroccopteryx are further related to the Australian taxa Ferrodraco and Mythunga, which are all grouped in a new clade: the Tropeognathinae. Our analysis suggests that morphological evolution within anhanguerids was quite more complex than previously thought, with coloborhynchines representing the oldest recorded lineage of Anhangueridae, which achieved a worldwide distribution at least from the Aptian to the Cenomanian.
Źródło:
Acta Palaeontologica Polonica; 2020, 65, 4; 743-761
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Bone Microstructure and Relative Age of the Holotype Specimen of the Diplodocoid Sauropod Dinosaur Suuwassea emilieae
Autorzy:
Hedrick, B.P.
Tumarkin-Deratzian, A.R.
Dodson, P.
Powiązania:
https://bibliotekanauki.pl/articles/945796.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
dinosauria
sauropoda
suuwassea
histology
jurassic
morrison formation
montana
usa
Opis:
We present the first study of bone microstructure in Suuwassea emilieae, a diplodocoid sauropod from the Morrison Formation. Although the holotype of Suuwassea was recently identified as a subadult, bone histology demonstrates that this individual had reached sexual maturity at approximately 75–80% of maximum adult size. The smaller size of the holotype of Suuwassea relative to contemporary sauropods is due to ontogeny rather than a true reflection of adult size. A fully adult individual would have likely been similar in size to a fully adult specimen of Apatosaurus. Suuwassea has a number of plesiomorphic characters that might have been explained by its supposed early ontogenetic status, and would then have called the validity of the taxon into question. However, our demonstration that it was an adult confirms that these features represent retention of plesiomorphic character states or evolutionary reversals in a derived animal. Additionally, the specimen shows extensive cortical drift and secondary osteon formation related to skeletal loading, which is often obscured by complete remodeling of Haversian systems in sauropod taxa. There are substantial differences in the microstructure across the bone, which could make histologic samples not based upon complete cross sections problematic. Suuwassea is one of four currently recognized dicraeosaurid taxa, and this study contributes potential taxonomic characters in sauropod bone microstructure.
Źródło:
Acta Palaeontologica Polonica; 2014, 59, 2; 295-304
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The osteoderm microstructure in doswelliids and proterochampsids and its implications for palaeobiology of stem archosaurs
Autorzy:
PONCE, DENIS A.
CERDA, IGNACIO A.
DESOJO, JULIA B.
NESBITT, STERLING J.
Powiązania:
https://bibliotekanauki.pl/articles/945925.pdf
Data publikacji:
2017
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
archosauria
doswelliidae
protero champ sidae
palaeoecology
microanatomy
histology
triassic
usa
Opis:
Osteoderms are common in most archosauriform lineages, including basal forms, such as doswelliids and proterochampsids. In this survey, osteoderms of the doswelliids Doswellia kaltenbachi and Vancleavea campi, and proterochampsid Chanaresuchus bonapartei are examined to infer their palaeobiology, such as histogenesis, age estimation at death, development of external sculpturing, and palaeoecology. Doswelliid osteoderms have a trilaminar structure: two cortices of compact bone (external and basal) that enclose an internal core of cancellous bone. In contrast, Chanaresuchus bonapartei osteoderms are composed of entirely compact bone. The external ornamentation of Doswellia kaltenbachi is primarily formed and maintained by preferential bone growth. Conversely, a complex pattern of resorption and redeposition process is inferred in Archeopelta arborensis and Tarjadia ruthae. Vancleavea campi exhibits the highest degree of variation among doswelliids in its histogenesis (metaplasia), density and arrangement of vascularization and lack of sculpturing. The relatively high degree of compactness in the osteoderms of all the examined taxa is congruent with an aquatic or semi-aquatic lifestyle. In general, the osteoderm histology of doswelliids more closely resembles that of phytosaurs and pseudosuchians than that of proterochampsids
Źródło:
Acta Palaeontologica Polonica; 2017, 62, 4; 819-831
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Late Cretaceous sharks Cretoxyrhina and Cardabiodon from Montana, USA
Autorzy:
Siverson, M
Lindgren, J.
Powiązania:
https://bibliotekanauki.pl/articles/22717.pdf
Data publikacji:
2005
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
shark
USA
Cretoxyrhina
Cretaceous
Late Cretaceous
Montana
biostratigraphy
Lamniformes
Cardabiodon
paleontology
Opis:
The middle part of the Cretaceous represents a time of high diversity and rapid rates of dental evolution in lamniform sharks. Several species had a very wide spatial distribution with recorded occurrences in both hemispheres. We have examined isolated teeth of Cretoxyrhina and Cardabiodon from eastern Russia, Mangyshlak in Kazakhstan, and the Western Interior of the USA. The material indicates that samples of isolated teeth of the two genera have high potential in intercontinental correlation of the upper Albian to mid−Turonian interval in mid−palaeolatitude deposits, poor in other age−diagnostic fossil groups. The utilization of these lamniforms in mid−Cretaceous biostratigraphy is currently hampered by the nearly total absence in the literature of well illustrated, well dated and sufficiently large samples of isolated teeth of the two genera. As a first step towards the establishment of an intercontinental elasmobranch zonation for mid−Cretaceous strata in temperate palaeo−regions, we describe and illustrate samples of teeth of Cardabiodon venator sp. nov. and Cretoxyrhina mantelli from the lower middle Turonian Collignoniceras woollgari regulare Zone in the Fairport Member of the Carlile Shale in east−central Montana, USA. These samples could serve as reference points for future biostratigraphic studies of Cretoxyrhina and Cardabiodon. The extinction of Cretoxyrhina may be diachronous, as regional last appearance data range from the upper Santonian (Marsupites testudinarius Zone) in Western Australia to the uppermost lower Campanian (informal Belemnellocamax mammillatus zone; a lateral equivalent to the German Gonioteuthis quadrata gracilis/Belemnitella mucronata Zone) in southern Sweden.
Źródło:
Acta Palaeontologica Polonica; 2005, 50, 2
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Globicephaline whales from the Mio-Pliocene Purisima Formation of central California, USA
Autorzy:
Boessenecker, R.W.
Perry, F.A.
Geisler, J.H.
Powiązania:
https://bibliotekanauki.pl/articles/945570.pdf
Data publikacji:
2015
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Mammalia
Cetacea
Odontoceti
Delphinidae
Globicephalinae
paleontology
Pliocene
Purisima Formation
California
USA
Opis:
Oceanic dolphins (Odontoceti: Delphinidae) constitute the most speciose family of extant cetaceans, yet their fossil record is limited. Although several extinct species are known from Mediterranean and North Atlantic localities, there are few examples from deposits along the Pacific Rim. Despite the rich record of successive marine mammal fossil assemblages in the extensively sampled eastern North Pacific, only one fossil delphinid, Protoglobicephala (Pliocene, Baja California), has been described. We report globicephaline remains from the Mio-Pliocene Purisima Formation of Northern California, including a partial cranium and two isolated petrosals. The skull exhibits large ridges on the premaxillae, and cannot be referred to any extant globicephaline genus. Similarly, the petrosals cannot be referred to any described delphinid genus, although they are most similar to those of Globicephala. Linear regression analyses demonstrate that promontorium length and bony nares width scale significantly within delphinidans, and provide a new method for testing referrals of isolated fossil odontocete petrosals to taxa known only by crania. Applying this method to the new globicephalines from the Purisima Formation, we find the petrosals to be too small to represent the same taxon as the skull, thus indicating the presence of two separate species. Our results demonstrate that globicephalines had achieved a worldwide distribution by the early Pliocene, suggesting diversification of the subfamily by 5 Ma.
Źródło:
Acta Palaeontologica Polonica; 2015, 60, 1; 113-122
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The first possible remingtonocetid stem whale from North America
Autorzy:
Uhen, M.D.
Peredo, C.M.
Powiązania:
https://bibliotekanauki.pl/articles/2082285.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Mammalia
Archaeocete
Remingtonocetidae
middle Eocene
Castle Hayne Formation
North Carolina
USA
Opis:
Remingtonocetid cetaceans are a group of stem whales known from the Indo-Pakistan and North African Tethys Ocean. An unusual tooth was discovered by Peter J. Harmatuk in 1973 in the middle Eocene Superior Stone Quarry (now the Martin Marietta Quarry) near Castle Hayne, North Carolina, USA. Here we identify this tooth as a premolar of a possible member of the Remingtonocetidae, which would extend the range of this family across the Atlantic to eastern North America. This partial tooth includes most of the crown (missing the mesial end) and the posterior root. The tooth bears a single central cusp and a worn accessory cusp on the posterior end. This tooth most closely resembles premolars of Remingtonocetus and is rather dissimilar to premolars of other archaeocetes known from the middle Eocene of North America, such as the families Protocetidae and Basilosauridae. This new record potentially expands the geographic distribution of the amphibious cetacean family Remingtonocetidae across the Atlantic.
Źródło:
Acta Palaeontologica Polonica; 2021, 66, 1; 77-83
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Exceptional cameral deposits in a sublethally injured Carboniferous orthoconic nautiloid from the Buckhorn Asphalt Lagerstatte in Oklahoma, USA
Autorzy:
Seuss, B.
Mapes, R.H.
Klug, C.
Nutzel, A.
Powiązania:
https://bibliotekanauki.pl/articles/22348.pdf
Data publikacji:
2012
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
cameral deposit
Carboniferous
orthoconic nautiloid
Buckhorn Asphalt
Oklahoma
USA
Nautiloidea
Pseudorthoceratidae
predation
sublethal damage
Opis:
The cameral and intrasiphonal deposits of a Pennsylvanian straight nautiloid (Pseudorthoceratidae) are studied in order to understand the formation of these deposits. The specimens from the Buckhorn Asphalt deposit (Oklahoma) are exceptionally preserved including original aragonite and microstructures. The specimen investigated survived a predation attempt and shows bite marks on the phragmocone. This is the second report of an ectocochleate cephalopod and first report of an orthoconic nautiloid which survived massive damage of conch and siphuncle. For the first time, a high−magnesium calcitic mineralogy of cameral deposits is documented. These deposits were formed in alternation with aragonite in a chamber which was perforated during the unsuccessful predation attempt. The animal formed the chamber deposits throughout its entire lifetime and the siphuncle played a major role in formation of the cameral deposits.
Źródło:
Acta Palaeontologica Polonica; 2012, 57, 2
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Palaeoecology of the Spathian Virgin Formation (Utah, USA) and its implications for the Early Triassic recovery
Autorzy:
Hofmann, R.
Hautmann, M.
Wasmer, M.
Bucher, H.
Powiązania:
https://bibliotekanauki.pl/articles/21319.pdf
Data publikacji:
2013
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
paleoecology
Spathian Virgin Formation
Utah
USA
Early Triassic
Triassic
recovery
diversity
biotic recovery
mass extinction
Opis:
The Spathian (late Early Triassic) Virgin Formation of south−western Utah (USA) yields a comparatively diverse benthic fauna that flourished ~2 Ma after the end−Permian mass extinction. In this study, we present quantitative palaeoecological data, which are analysed in the context of depositional environments. This integrated approach helps to discriminate between effects of the end−Permian mass extinction event and local environmental factors on alpha diversity and ecological structure of the Virgin Fauna. Shallow subtidal environments yield the highest species richness and lowest dominance val− ues as recorded in two benthic associations, the Eumorphotis ericiusAssociation and the Protogusarella smithi Association, both ofwhich contain 20 benthic species (bivalves, gastropods, brachiopods, echinoderms, and porifers). Tidal inlet deposits yield a low diverse fauna (Piarorhynchella triassica Association) with a very high dominance of filter feeders adapted to high energy conditions.Another comparably low diverse fauna is recorded by the Bakevellia exporrecta Association, which occurs in deposits of the offshore transition zone,most likely reflecting unconsolidated substrates. A single sample contain− ing five bivalve species (Bakevellia costata Assemblage) is recorded from a marginal−marine setting. The Virgin fauna yields a bulk diversity of 30 benthic species (22 genera) of body fossils and 14 ichnogenera and, thus, represents the most di− verse marine bottom fauna known so far from the Early Triassic. Our results suggest that oceanographic conditions during the early Spathian enabled ecosystems to rediversify without major abiotic limitations. However, taxonomical differentia− tion between habitats was still low, indicating a time lag between increasing within−habitat diversity (alpha diversity) and the onset of taxonomical differentiation between habitats (beta diversity). We suggest that taxonomical habitat differentia− tion after mass extinction events starts only when within−habitat competition exceeds a certain threshold, which was not yet reached in the Spathian of the investigated area. This interpretation is an alternative to previous suggestions that the preva− lence of generalistic taxa in the aftermath of mass extinction events reflects protracted environmental stress. The onset of in− creasing beta diversity is a potential criterion for distinguishing two major recovery phases, the first ending with habitat satu− ration and the second ending with the completion of ecosystem differentiation.
Źródło:
Acta Palaeontologica Polonica; 2013, 58, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Late Oligocene sharks and rays from the Chandler Bridge Formation, Dorchester County, South Carolina, USA
Autorzy:
Cicimurri, D.J.
Knight, J.L.
Powiązania:
https://bibliotekanauki.pl/articles/21710.pdf
Data publikacji:
2009
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Late Oligocene
Oligocene
shark
ray
Chandler Bridge Formation
Dorchester County
South Carolina
USA
Chondrichthyes
Neoselachii
Opis:
A diverse vertebrate fauna, dominated by elasmobranch taxa, was collected from the upper Oligocene (Chattian) Chandler Bridge Formation in Summerville, Dorchester County, South Carolina. Nearly 3,500 teeth and dermal denticles are assigned to 29 species of sharks and rays, and our sample includes the oldest known occurrence of the whale shark, Rhincodon, as well as a new skate, Raja mccollumi sp. nov. The Chandler Bridge elasmobranch assemblage is comparable in species diversity to Chattian assemblages of Virginia and North Carolina, USA, and Germany. Notable absences from Germany include Rhincodon, Hemipristis, and Sphyrna zygaena, likely reflecting the influence of colder water on the North Sea Basin during the Chattian. Squaloids, pristiophoroids, and hexanchoids are known from Chattian deposits of the Albemarle Embayment (North Carolina), Salisbury Embayment (Virginia), and North Sea Basin, but these taxa are absent from the Chandler Bridge assemblage, perhaps because of shallow, warm water (20 to 25°C) conditions within the more southerly Charleston Embayment.
Źródło:
Acta Palaeontologica Polonica; 2009, 54, 4
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Chaetognath grasping spines from the Upper Mississippian of Arkansas [USA]
Autorzy:
Doguzhaeva, L A
Mutvel, H.
Mapes, R.H.
Powiązania:
https://bibliotekanauki.pl/articles/23070.pdf
Data publikacji:
2002
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
grasping spine
fossil
USA
protoconodont
organic spine
phosphatized fossil
morphology
Arkansas
ultrastructure
Chaetognatha
paleontology
chaetognath
Opis:
Previously unidentified tiny (about 0.5 mm in length), hollow, gently curved, serrated spines probably originally composed of horny, organic fibers from the Upper Mississippian (Middle Chesterian = Namurian A equivalent or lower Serpukhovian) of Arkansas (USA) are described, and their probable chaetognath affinities are discussed. The specimens are preserved in an oval accumulation (about 15 mm long and 6 mm wide) of approximately 200 specimens within a small (about 25 mm in length) phosphatic concretion. For comparison, the grasping spines of the Recent chaetognath Eukrohnia hamata were examined. The Arkansas specimens are named Eoserratosagitta serrata gen. et sp. nov., and this genus is assigned to the Phylum Chaetognatha. The Upper Mississippian spines are also compared with protoconodonts. This comparison supports the hypothesis that the chaetognaths may have existed in the Cambrian.
Źródło:
Acta Palaeontologica Polonica; 2002, 47, 3
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A new ankylosaurid from the Late Cretaceous Two Medicine Formation of Montana, USA
Autorzy:
Penkalski, P.
Powiązania:
https://bibliotekanauki.pl/articles/945878.pdf
Data publikacji:
2014
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
ankylosaur
Dinosauria
Ornithischia
Ankylosauridae
systematics
paleontology
Campanian
Late Cretaceous
Cretaceous
Two Medicine Formation
Montana
USA
Opis:
Oohkotokia horneri gen. et sp. nov. is described based on a specimen in the collections of the Museum of the Rockies, Montana, USA. Oohkotokia exhibits a unique combination of characters not seen in other late Campanian North American ankylosaurids: prominent, horn-like, trihedral squamosal bosses, a small, undistinguished median nasal plate on the dorsal surface of the rostrum, a relatively small occipital condyle, a smooth, finely pitted osteoderm external texture, and triangular lateral osteoderms. Other specimens from the Two Medicine Formation are referable to Oohkotokia. O. horneri, Euoplocephalus tutus, Dyoplosaurus acutosquameus, and Scolosaurus cutleri separate stratigraphically.
Źródło:
Acta Palaeontologica Polonica; 2014, 59, 3; 617-634
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Multi-snail infestation of Devonian crinoids and the nature of platyceratid-crinoid interactions
Autorzy:
Baumiller, T K
Powiązania:
https://bibliotekanauki.pl/articles/20265.pdf
Data publikacji:
2002
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
USA
Silica Formation
Devonian
platyceratid-crinoid interaction
biotic interaction
crinoid
snail
Middle Devonian
paleontology
Ohio
Opis:
The well−known association of platyceratid snails and crinoids typically involves a single snail positioned on the tegmen of the crinoid host; this has led to the inference of coprophagy. Two specimens of the camerate crinoid Arthroacantha from the Middle Devonian Silica Formation of Ohio, USA, exhibit numerous snails on their tegmens. On one of these, 6 platyceratid juveniles of approximately equal size are found on the tegmen. On the second crinoid, the largest of 7 infesting platyceratids occupies the typical position over the anal vent while others are either superposed (tiered) upon it or are positioned elsewhere on the tegmen. These specimens illustrate that platyceratids (1) settled on crinoids as spat, (2) were not strictly coprophagous during life yet (3) benefited from a position over the anal vent.
Źródło:
Acta Palaeontologica Polonica; 2002, 47, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Early Pennsylvanian xenacanth chondrichthyans from the Swisshelm Mountains, Arizona, USA
Autorzy:
Johnson, G.D.
Thayer, D.W.
Powiązania:
https://bibliotekanauki.pl/articles/21790.pdf
Data publikacji:
2009
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
vertebrate
fauna
xenacanth chondrichthyan
chondrichthyan
Swisshelm Mountains
Arizona
USA
Chondrichthyes
Xenacanthiformes
Bransonelliformes
Orthacanthus
Triodus
Bransonella
Opis:
Three genera of xenacanths, based on isolated teeth, occur in the lepospondyl (amphibian)−dominated fauna from the upper Black Prince Limestone (late Bashkirian). Orthacanthus donnelljohnsi sp. nov. teeth, with carinae lacking serrations on the compressed principal cusps, and only one intermediate cusp, represent both adult and juvenile teeth. Heterodonty occurs in both adult and juvenile dentitions. The absence of serrations is unique among Pennsylvanian species of Orthacanthus. Teeth with often highly asymmetrical bases with an aborally−flexed lingual marginal flange (= anterolingual shelf) and a single intermediate cusp are assigned to Triodus elpia sp. nov. A central foramen occurs in the base, unlike most other species; the moderately compressed principal cusps bear generally straight cristae. They represent the first reported occurrence of Triodus in the Paleozoic of North America. Five teeth, with cristae extending from the cusps onto their bases, belong to Bransonella. Two are questionably assigned to Bransonella nebraskensis, one to B. ?lingulata with its labio−lingually elongated apical button and smaller than normal intermediate cusp, and one each to Bransonella sp. “A” and “B”. Bransonella sp. “A” has a base wider (labio−lingual) than long, the reverse of the other Bransonella teeth. Bransonella sp. “B” is distinctly different, as it lacks an intermediate cusp (as in some B. lingulata teeth), and the basal tubercle is beneath one of the cusps (with no evidence of deformity).
Źródło:
Acta Palaeontologica Polonica; 2009, 54, 4
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Cranial morphology, systematics and succession of beavers from the middle Miocene Valentine Formation of Nebraska, USA
Autorzy:
Korth, W W
Powiązania:
https://bibliotekanauki.pl/articles/21878.pdf
Data publikacji:
2008
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
Miocene
beaver
systematics
Valentine Formation
paleontology
fauna succession
cranial morphology
USA
Castoridae
Barstovian
Clarendonian
Middle Miocene
Nebraska
Opis:
Previously, it was believed that there was a dramatic turn−over in the fauna of beavers (Rodentia, Castoridae) from the Barstovian to the Clarendonian from Nebraska. Stratigraphically controlled collections of fossil castorids from the Valentine Formation, which cross this boundary, now indicate that a complete change in the castorid fauna did not occur, but instead a more gradual change and replacement of earlier taxa with more advanced taxa occurred. The range of Eucastor tortus and Monosaulax skinneri is extended from late Barstovian into the latest Barstovian Devil’s Gulch Member and the range of the otherwise Clarendonian species of Prodipoides is extended downward into the late Barstovian Crookston Bridge Member. The skulls of Monosaulax skinneri and Eucastor valentinensis are described in detail for the first time. The cranial morphology of M. skinneri is primitive for Castoroidini and that of E. valentinensis is specialized for tooth−digging behavior as in the Nothodipoidini. A new genus, Temperocastor, is proposed for E. valentinensis based on its primitive morphology of the cheek teeth and derived cranial morphology. Temperocastor represents the most primitive nothodipoidine.
Źródło:
Acta Palaeontologica Polonica; 2008, 53, 2
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Morphology and histology of dorsal spines of the xenacanthid shark Orthacanthus platypternus from the Lower Permian of Texas, USA: palaeobiological and palaeoenvironmental implications
Autorzy:
Beck, K.G.
Soler-Gijon, R.
Carlucci, J.R.
Willis, R.E.
Powiązania:
https://bibliotekanauki.pl/articles/21629.pdf
Data publikacji:
2016
Wydawca:
Polska Akademia Nauk. Instytut Paleobiologii PAN
Tematy:
morphology
histology
dorsal spine
xenacanthid shark
shark
Orthacanthus platypterus
Chondrichthyes
Xenacanthiformes
Lower Permian
Texas
USA
paleobiology
paleoenvironment
Opis:
Detailed studies on Carboniferous species of the xenacanth Orthacanthus have shown that the xenacanth dorsal fin spine can be used for skeletochronological analyses and provides valuable information about development, growth and environmental life conditions of those extinct sharks. We report here for the first time the histology and skeletochronology of Permian specimens, dorsal spines of Orthacanthus platypternus from the Craddock Bone Bed (lower Clear Fork Formation; Early Permian, Leonardian age) of northern Baylor County (north-central Texas, USA). Twelve dorsal spines of O. platypternus preserve a highly vascularized wall mainly composed of centrifugally growing dentine in a succession of dentine layers, probably deposited with an annual periodicity. As expected, spines of individuals with 1–2 dentine layers, presumably juveniles, present the smallest sizes. However, spines of individuals showing at least 3–4 dentine layers and interpreted to be subadults/young adults, are distributed in two spine-size clusters corresponding to females (probably the largest spines) and males, in agreement with the hypothesis of sexual size dimorphism proposed in a previous biometric analysis. Our comparative study of O. platypternus and the Stephanian species O. meridionalis further suggests that spine denticulation can be useful for distinguishing between species of Orthacanthus and sexually dimorphic forms (juvenile to adults) in each species. Total body length estimations of O. platypternus from the Craddock Bone Bed point to relatively large juveniles and small subadults/young adults (less than 2 m in total length), living as opportunistic predators in the pond-channel coastal plain environments represented by the bone bed deposits. The comparative analyses of the ontogenetic stages of the recorded specimens of O. platypternus and their distribution along different facies and localities indicate that this species was euryhaline, diadromous with a catadromous life-cycle which was strongly regulated by the semi-arid, seasonally dry tropical climate affecting western Pangaea during the Early Permian.
Źródło:
Acta Palaeontologica Polonica; 2016, 61, 1
0567-7920
Pojawia się w:
Acta Palaeontologica Polonica
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 24

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