scholarly journals Enamel microstructure in Exaeretodon, a Late Triassic South American traversodontid (Therapsida: Cynodontia)

2007 ◽  
Vol 10 (2) ◽  
pp. 71-78 ◽  
Author(s):  
Fernando Abdala
Keyword(s):  
Late Triassic ◽  
South American ◽  
Enamel Microstructure

The oldest South American ichthyosaur from the late Triassic of northern Chile

1992 ◽  
Vol 129 (2) ◽  
pp. 247-249 ◽  
Author(s):  
M. Suarez ◽  
C. M. Bell
Keyword(s):  
South America ◽  
Late Triassic ◽  
South American ◽  
Northern Chile ◽  
Specific Level ◽  
Shallow Marine

AbstractIchthyosaur remains found in late Triassic shallow marine limestones in Quebrada Doña Inés Chica (latitude 26° 07′ S; longitude 69° 20′ W), northern Chile, are the oldest known ichthyosaur fossils from Central and South America. The previous oldest South American ichthyosaur was recorded in Hettangian rocks, also from northern Chile. The fossils comprise five worn teeth, one paddle bone and one scapula or humerus fragment, all collected from a single bed at the same locality. Although the material has not been identified to a generic or specific level, its presence alone broadens the knowledge of the distribution and habitat of Triassic ichthyosaurs. Late Triassic ammonites and brachiopods in the same stratum provide the age control.

African origin of caviomorph rodents is indicated by incisor enamel microstructure

Paleobiology ◽  
1994 ◽  
Vol 20 (1) ◽  
pp. 5-13 ◽  
Author(s):  
Thomas Martin
Keyword(s):  
North American ◽  
Late Eocene ◽  
South American ◽  
Late Oligocene ◽  
African Origin ◽  
Enamel Microstructure ◽  
The North ◽  
Early Oligocene ◽  
Caviomorph Rodents

The same three subtypes of derived multiserial Hunter-Schreger bands are found in the incisor enamel of African phiomorph rodents from the late Eocene-early Oligocene and the oldest South American Caviomorpha from the Deseadan (late Oligocene). The synapomorphies contained therein, especially arrangement and orientation of interprismatic matrix, make an African origin of the Caviomorpha very probable. A North American origin of the Caviomorpha is thus rejected, as only primitive pauciserial Hunter-Schreger bands have been observed in possible ischyromyoid caviomorph ancestors. A multiserial Schmelzmuster apparently never evolved in the North American rodent fauna.

South American occurrences of the Adamanian (Late Triassic: Latest Carnian) index taxon Stagonolepis (Archosauria: Aetosauria) and their biochronological significance

2002 ◽  
Vol 76 (5) ◽  
pp. 852-863 ◽  
Author(s):  
Andrew B. Heckert ◽  
Spencer G. Lucas
Keyword(s):  
North America ◽  
Late Triassic ◽  
Eastern North America ◽  
Appendicular Skeleton ◽  
South American ◽  
Western North America ◽  
Newark Supergroup ◽  
Land Vertebrate ◽  
Santa Maria ◽  
Apparent Age

Aetosaur fossils from the Upper Triassic Ischigualasto Formation of Argentina formerly assigned to Aetosauroides scagliai Casamiquela and Argentinosuchus bonapartei Casamiquela are reassigned to Stagonolepis robertsoni Agassiz (small specimens) and S. wellesi (Long and Ballew) (larger specimens). Numerous features of the skull, vertebral column, appendicular skeleton, and particularly the armor, of these Argentinian aetosaurs are identical to those of Stagonolepis and differ from other aetosaurs. Identification of Stagonolepis in South America has important implications for the correlation of nonmarine strata across Late Triassic Pangea. Stagonolepis is an index taxon of the Adamanian land-vertebrate faunachron of latest Carnian age. Its occurrences in the Ischigualasto and Santa Maria formations, as well as at the type locality in the Lossiemouth Sandstone of Scotland and in the Blasensandstein of the German Keuper, cross-correlate with a well-established tetrapod biostratigraphy of the Chinle Group in western North America. Thus, all Stagonolepis records are of Adamanian (latest Carnian) age, not Otischalkian (early or “middle” Carnian) age, as proposed by some earlier workers. This correlation also demonstrates that the oldest known dinosaurs are not from the Ischigualasto and Santa Maria formations. Previous workers obtained radioisotopic dates of 227.8 Ma from the Ischigualasto Formation, providing a maximum numerical date for Stagonolepis-bearing units. This date must be late Carnian, not of Ladinian age, and thus supports the apparent age of the Ladinian-Carnian boundary (232 Ma) of time scales based on the Newark Supergroup in eastern North America.

scholarly journals Two New Cynodonts (Therapsida) from the Middle-Early Late Triassic of Brazil and Comments on South American Probainognathians

PLoS ONE ◽  
2016 ◽  
Vol 11 (10) ◽  
pp. e0162945 ◽  
Author(s):  
Agustín G. Martinelli ◽  
Marina Bento Soares ◽  
Cibele Schwanke
Keyword(s):  
Late Triassic ◽  
South American ◽  
Early Late

Systematics and paleobiogeography of Late TriassicGryphaea(Bivalvia) from the North American Cordillera

1992 ◽  
Vol 66 (1) ◽  
pp. 28-39 ◽  
Author(s):  
Christopher A. Mcroberts
Keyword(s):  
North American ◽  
Late Triassic ◽  
South American ◽  
Long Distance ◽  
Low Latitude ◽  
North American Cordillera ◽  
The North ◽  
North American Craton ◽  
Far Eastern ◽  
North And South

Evaluation of previously undescribed collections of Late TriassicGryphaeafrom the North American Cordillera increases the temporal range and geographic distribution of the genus.Gryphaea(Gryphaea)arcuataeformisKiparisova,G.cf.G.(Gryphaea)keilhauiBöhm, and a new species,G.(Gryphaea)nevadensis, occur in lower Carnian to upper Norian strata from Alaska, British Columbia, Oregon, and Nevada. The distribution is mostly primary with respect to the Upper Triassic North American Craton, and requires long-distance larval dispersal along the latitude of far-eastern Panthalassa. Unlike most modern oysters, the distribution of these Triassic gryphaeids may have been restricted to cool and deeper water environments.An early Carnian age ofGryphaea(Gryphaea)arcuataeformisplaces this species as the oldest knownGryphaea. When combined with late Carnian and Norian occurrences from the North and South American Cordillera, these data indicate that a low-latitude origin for the genus cannot be overlooked. Gryphaeids survived the end-Triassic extinction event presumably by living in refugia.

A new aetosaur genus (Archosauria: Pseudosuchia) from the early Late Triassic of southern Brazil

Zootaxa ◽  
2012 ◽  
Vol 3166 (1) ◽  
pp. 1 ◽  
Author(s):  
JULIA B. DESOJO ◽  
MARTÍN D. EZCURRA ◽  
EDIO E. KISCHLAT
Keyword(s):  
Cervical Vertebrae ◽  
Cladistic Analysis ◽  
Axial Skeleton ◽  
Late Triassic ◽  
South American ◽  
Southern Brazil ◽  
Caudal Vertebra ◽  
Caudal Vertebrae ◽  
Santa Maria ◽  
Early Late

We describe the new aetosaur Aetobarbakinoides brasiliensis gen. et sp. nov. from the early Late Triassic (late Carnian-early Norian) Brazilian Santa Maria Formation. The holotype is composed of a partial postcranium including several cer-vical and dorsal vertebrae and ribs, one anterior caudal vertebra, right scapula, right humerus, right tibia, partial right pes,and anterior and mid-dorsal paramedian osteoderms. Aetobarbakinoides is differentiated from other aetosaurs by the pres-ence of cervical vertebrae with widely laterally extended prezygapophyses, mid-cervical vertebrae with anterior articularfacet width more than 1.2 times wider than the posterior one, anterior caudal vertebrae with extremely anteroposteriorlyshort prezygapophyses, elongated humerus and tibia in relation to the axial skeleton, and paramedian osteoderms with aweakly raised anterior bar. A cladistic analysis recovered the new species as more derived than the South American generaAetosauroides (late Carnian-early Norian) and Neoaetosauroides (late Norian-Rhaetian), and it is nested as the sister-tax-on of an unnamed clade, composed of Typothoracisinae and Desmatosuchinae, due to the absence of a ventral keel in thecervical vertebrae. Aetobarbakinoides presents a skeletal anatomy previously unknown among South American aetosaurs,with the combination of presacral vertebrae with hyposphene, anteroposteriorly short and unkeeled cervical vertebrae,gracile limbs, and paramedian osteoderms with a weakly raised anterior bar. Aetobarbakinoides is among the oldest knownaetosaurs together with Aetosauroides from Argentina and Brazil and Stagonolepis robertsoni from Scotland, indicatinga widely distributed early record for the group. In addition, the recognition of a suite of derived features in Aetobarbaki-noides, which is one of the oldest known aetosaurs, is in agreement with an older origin for the group, as it is expected by the extensive ghost lineages at the base of the main pseudosuchian clades.

scholarly journals Anatomical notes and discussion of the first described aetosaurStagonolepis robertsoni(Archosauria: Suchia) from the Upper Triassic of Europe, and the use of plesiomorphies in aetosaur biochronology

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5455 ◽  
Author(s):  
William G. Parker
Keyword(s):  
Upper Triassic ◽  
Late Triassic ◽  
South American ◽  
Cervical Rib ◽  
Holotype Specimen ◽  
Surface Ornamentation ◽  
North And South ◽  
Detailed Work

Stagonolepis robertsoni, from the Late Triassic of Scotland, was the first named aetosaurian. Known mostly from a series of natural molds from two localities, the osteology of this taxon has been difficult to interpret. Detailed work on this material in the late 1950s resulted in a monograph that set the standard for the understanding of aetosaurians, makingStagonolepis robertsonithe best known aetosaurian; however, little has been done with this material since. Reanalysis of this material shows that despite its limitations the early 1960s reconstruction work depicts the preserved characteristics faithfully, especially in the skull. The first cervical rib is extremely anteroposteriorly elongate as inAlligator, a character not previously recognized in aetosaurians. Diapophyseal and zygapophyseal vertebral laminae are present in the cervical and trunk vertebrae. The ilium is autapomorphic with distinct pre- and post-processes of the iliac blade. The osteoderms differ from North and South American material that has been ascribed to the genus. Those assignments are based on plesiomorphies within Aetosauria, such as a radial ornamentation and a posteriorly located and medially offset dorsal eminence. Biostratigraphic correlations using taxonomic conclusions based on plesiomorphic characters should not be used. The holotype specimen ofS. robertsoniis currently diagnostic, in part because ventral osteoderms are not known for many aetosaurian taxa and the surface ornamentation of randomly distributed, closely packed oblong pits found inS. robertsoniis unique within Aetosauria.

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