scholarly journals Insight on the anatomy, systematic relationships, and age of the Early Cretaceous ankylopollexian dinosaur Dakotadon lakotaensis

2015 ◽  
Author(s):  
Clint A Boyd ◽  
Darrin C Pagnac
Keyword(s):  
North America ◽  
Early Cretaceous ◽  
Original Description ◽  
Field Work ◽  
Optimality Criteria ◽  
Dorsal Vertebra ◽  
Caudal Vertebrae ◽  
Systematic Relationships ◽  
Preparation Work ◽  
Extensive Deformation

Knowledge regarding the early evolution within the dinosaurian clade Ankylopollexia drastically increased over the past two decades, in part because of an increase in described taxa from the Early Cretaceous of North America. These advances motivated the recent completion of extensive preparation and conservation work on the holotype and only known specimen of Dakotadon lakotaensis, a basal ankylopollexian from the Lakota Formation of South Dakota. That specimen (SDSM 8656) preserves a partial skull, lower jaws, a single dorsal vertebra, and two caudal vertebrae. That new preparation work exposed several bones not included in the original description and revealed that other bones were previously misidentified. The presence of extensive deformation in areas of the skull is also noted that influenced inaccuracies in prior descriptions and reconstructions of this taxon. In addition to providing an extensive re-description of D. lakotaensis, this study reviews previously proposed diagnoses for this taxon, identifies three autapomorphies, and provides an extensive differential diagnosis. Dakotadon lakotaensis is distinct from the only other ankylopollexian taxon known from the Lakota Formation, Osmakasaurus depressus, in the presence of two prominent, anteroposteriorly oriented ridges on the ventral surfaces of the caudal vertebrae, the only overlapping material preserved between these taxa. The systematic relationships of Dakotadon lakotaensis are evaluated using both the parsimony and posterior probability optimality criteria, with both sets of analyses recovering D. lakotaensis as a non-hadrosauriform ankylopollexian that is more closely related to taxa from the early Cretaceous (e.g., Iguanacolossus, Hippodraco, and Theiophytalia) than to more basally situated taxa from the Jurassic (e.g., Camptosaurus, Uteodon). This taxonomic work is supplemented by field work that relocated the type locality, confirming its provenance from unit L2 (lower Fuson Member equivalent) of the Lakota Formation. Those data, combined with recently revised ages for the members of the Lakota Formation based on charophyte and ostracod biostratigraphy, constrain the age of this taxon to the late Valanginian to early Hauterivian. The only other equivalent-aged ankylopollexian taxon from North America, the poorly known Planicoxa venenica from the Poison Strip Sandstone of Utah, preserves caudal vertebrae that bear the same ventral ridges seen in D. lakotaensis, raising the possibility of a close affinity between these taxa.

scholarly journals Insight on the anatomy, systematic relationships, and age of the Early Cretaceous ankylopollexian dinosaur Dakotadon lakotaensis

2015 ◽  
Author(s):  
Clint A Boyd ◽  
Darrin C Pagnac
Keyword(s):  
Early Cretaceous ◽  
Original Description ◽  
Field Work ◽  
Optimality Criteria ◽  
Dorsal Vertebra ◽  
The Past ◽  
Caudal Vertebrae ◽  
Systematic Relationships ◽  
Preparation Work ◽  
Extensive Deformation

Knowledge regarding the early evolution within the dinosaurian clade Ankylopollexia drastically increased over the past two decades, in part because of an increase in described taxa from the Early Cretaceous of North America. These advances motivated the recent completion of extensive preparation and conservation work on the holotype and only known specimen of Dakotadon lakotaensis, a basal ankylopollexian from the Lakota Formation of South Dakota. That specimen (SDSM 8656) preserves a partial skull, lower jaws, a single dorsal vertebra, and two caudal vertebrae. That new preparation work exposed several bones not included in the original description and revealed that other bones were previously misidentified. The presence of extensive deformation in areas of the skull is also noted that influenced inaccuracies in prior descriptions and reconstructions of this taxon. In addition to providing an extensive re-description of D. lakotaensis, this study reviews previously proposed diagnoses for this taxon, identifies two autapomorphies, and provides an extensive differential diagnosis. Dakotadon lakotaensis is distinct from the only other ankylopollexian taxon known from the Lakota Formation, Osmakasaurus depressus, in the presence of two prominent, anteroposteriorly oriented ridges on the ventral surfaces of the caudal vertebrae, the only overlapping material preserved between these taxa. The systematic relationships of D. lakotaensis are evaluated using both the parsimony and posterior probability optimality criteria, with both sets of analyses recovering D. lakotaensis as a non-hadrosauriform ankylopollexian that is more closely related to taxa from the Early Cretaceous (e.g., Iguanacolossus, Hippodraco, and Theiophytalia) than to more basally situated taxa from the Jurassic (e.g., Camptosaurus, Uteodon). This taxonomic work is supplemented by field work that relocated the type locality, confirming its provenance from unit L2 (lower Fuson Member equivalent) of the Lakota Formation. Those data, combined with recently revised ages for the members of the Lakota Formation based on charophyte and ostracod biostratigraphy, constrain the age of this taxon to the late Valanginian to early Barremian.

scholarly journals Insight on the anatomy, systematic relationships, and age of the Early Cretaceous ankylopollexian dinosaurDakotadon lakotaensis

PeerJ ◽  
2015 ◽  
Vol 3 ◽  
pp. e1263 ◽  
Author(s):  
Clint A. Boyd ◽  
Darrin C. Pagnac
Keyword(s):  
Early Cretaceous ◽  
Original Description ◽  
Field Work ◽  
Optimality Criteria ◽  
Dorsal Vertebra ◽  
The Past ◽  
Caudal Vertebrae ◽  
Systematic Relationships ◽  
Preparation Work ◽  
Extensive Deformation

Knowledge regarding the early evolution within the dinosaurian clade Ankylopollexia drastically increased over the past two decades, in part because of an increase in described taxa from the Early Cretaceous of North America. These advances motivated the recent completion of extensive preparation and conservation work on the holotype and only known specimen ofDakotadon lakotaensis, a basal ankylopollexian from the Lakota Formation of South Dakota. That specimen (SDSM 8656) preserves a partial skull, lower jaws, a single dorsal vertebra, and two caudal vertebrae. That new preparation work exposed several bones not included in the original description and revealed that other bones were previously misidentified. The presence of extensive deformation in areas of the skull is also noted that influenced inaccuracies in prior descriptions and reconstructions of this taxon. In addition to providing an extensive re-description ofD. lakotaensis, this study reviews previously proposed diagnoses for this taxon, identifies two autapomorphies, and provides an extensive differential diagnosis.Dakotadon lakotaensisis distinct from the only other ankylopollexian taxon known from the Lakota Formation,Osmakasaurus depressus, in the presence of two prominent, anteroposteriorly oriented ridges on the ventral surfaces of the caudal vertebrae, the only overlapping material preserved between these taxa. The systematic relationships ofD. lakotaensisare evaluated using both the parsimony and posterior probability optimality criteria, with both sets of analyses recoveringD. lakotaensisas a non-hadrosauriform ankylopollexian that is more closely related to taxa from the Early Cretaceous (e.g.,Iguanacolossus,Hippodraco, andTheiophytalia) than to more basally situated taxa from the Jurassic (e.g.,Camptosaurus, Uteodon). This taxonomic work is supplemented by field work that relocated the type locality, confirming its provenance from unit L2 (lower Fuson Member equivalent) of the Lakota Formation. Those data, combined with recently revised ages for the members of the Lakota Formation based on charophyte and ostracod biostratigraphy, constrain the age of this taxon to the late Valanginian to early Barremian.

scholarly journals Insight on the anatomy, systematic relationships, and age of the Early Cretaceous ankylopollexian dinosaur Dakotadon lakotaensis

2015 ◽  
Author(s):  
Clint A Boyd ◽  
Darrin C Pagnac
Keyword(s):  
Early Cretaceous ◽  
Original Description ◽  
Field Work ◽  
Optimality Criteria ◽  
Dorsal Vertebra ◽  
The Past ◽  
Caudal Vertebrae ◽  
Systematic Relationships ◽  
Preparation Work ◽  
Extensive Deformation

Knowledge regarding the early evolution within the dinosaurian clade Ankylopollexia drastically increased over the past two decades, in part because of an increase in described taxa from the Early Cretaceous of North America. These advances motivated the recent completion of extensive preparation and conservation work on the holotype and only known specimen of Dakotadon lakotaensis, a basal ankylopollexian from the Lakota Formation of South Dakota. That specimen (SDSM 8656) preserves a partial skull, lower jaws, a single dorsal vertebra, and two caudal vertebrae. That new preparation work exposed several bones not included in the original description and revealed that other bones were previously misidentified. The presence of extensive deformation in areas of the skull is also noted that influenced inaccuracies in prior descriptions and reconstructions of this taxon. In addition to providing an extensive re-description of D. lakotaensis, this study reviews previously proposed diagnoses for this taxon, identifies two autapomorphies, and provides an extensive differential diagnosis. Dakotadon lakotaensis is distinct from the only other ankylopollexian taxon known from the Lakota Formation, Osmakasaurus depressus, in the presence of two prominent, anteroposteriorly oriented ridges on the ventral surfaces of the caudal vertebrae, the only overlapping material preserved between these taxa. The systematic relationships of D. lakotaensis are evaluated using both the parsimony and posterior probability optimality criteria, with both sets of analyses recovering D. lakotaensis as a non-hadrosauriform ankylopollexian that is more closely related to taxa from the Early Cretaceous (e.g., Iguanacolossus, Hippodraco, and Theiophytalia) than to more basally situated taxa from the Jurassic (e.g., Camptosaurus, Uteodon). This taxonomic work is supplemented by field work that relocated the type locality, confirming its provenance from unit L2 (lower Fuson Member equivalent) of the Lakota Formation. Those data, combined with recently revised ages for the members of the Lakota Formation based on charophyte and ostracod biostratigraphy, constrain the age of this taxon to the late Valanginian to early Barremian.

Ordosemys leios, n.gen., n.sp., a new turtle from the Early Cretaceous of the Ordos Basin, Inner Mongolia

1993 ◽  
Vol 30 (10) ◽  
pp. 2128-2138 ◽  
Author(s):  
Donald B. Brinkman ◽  
Jiang-Hua Peng
Keyword(s):  
Early Cretaceous ◽  
Inner Mongolia ◽  
Cervical Vertebrae ◽  
Ordos Basin ◽  
Sister Group ◽  
Sister Group Relationship ◽  
Articular Surfaces ◽  
Caudal Vertebrae ◽  
The Ordos Basin

Ordosemys leios, n.gen., n.sp., from the Early Cretaceous Luohandong Formation, Zhidan Group, Ordos Basin, Inner Mongolia, is a primitive aquatic turtle with a reduced, fenestrated plastron. It shares with the members of the Centrocryptodira the presence of well-formed articular surfaces on the cervical and caudal vertebrae. Within the Centrocryptodira, characters of the cervical vertebrae suggest it is more closely related to the Polycryptodira than is the Meiolaniidae. Ordosemys shares with the Chelydridae the presence of two procoelous anterior caudals, but this character may be primitive for the Polycryptodira. Characters of the basicranial region of the braincase shared by Ordosemys and the Chelonioidea support a sister-group relationship between these two taxa, but a sister-group relationship between Ordosemys and the Polycryptodira is more strongly supported by characters shared by the Chelonioidea and other members of the Polycryptodira.

New multituberculate mammal from the Early Cretaceous of eastern North America

2013 ◽  
Vol 50 (3) ◽  
pp. 315-323 ◽  
Author(s):  
Richard L. Cifelli ◽  
Cynthia L. Gordon ◽  
Thomas R. Lipka
Keyword(s):  
North America ◽  
Iberian Peninsula ◽  
Early Cretaceous ◽  
North American ◽  
Lower Cretaceous ◽  
Late Jurassic ◽  
Relative Length ◽  
Central Position ◽  
Eastern North America ◽  
The North

Multituberculates, though among the most commonly encountered mammalian fossils of the Mesozoic, are poorly known from the North American Early Cretaceous, with only one taxon named to date. Herein we describe Argillomys marylandensis, gen. et sp. nov., from the Early Cretaceous of Maryland, based on an isolated M2. Argillomys represents the second mammal known from the Arundel Clay facies of the Patuxent Formation (Lower Cretaceous: Aptian). Though distinctive in its combination of characters (e.g., enamel ornamentation consisting of ribs and grooves only, cusp formula 2:4, presence of distinct cusp on anterobuccal ridge, enlargement of second cusp on buccal row, central position of ultimate cusp in lingual row, great relative length), the broader affinities of Argillomys cannot be established because of non-representation of the antemolar dentition. Based on lack of apomorphies commonly seen among Cimolodonta (e.g., three or more cusps present in buccal row, fusion of cusps in lingual row, cusps strongly pyramidal and separated by narrow grooves), we provisionally regard Argillomys as a multituberculate of “plagiaulacidan” grade. Intriguingly, it is comparable in certain respects to some unnamed Paulchoffatiidae, a family otherwise known from the Late Jurassic – Early Cretaceous of the Iberian Peninsula.

The Currently Earliest Angiosperm Fruit from the Jurassic of North America

2021 ◽  
Vol 2 (4) ◽  
Author(s):  
Xin Wang
Keyword(s):  
North America ◽  
Early Cretaceous ◽  
Middle Jurassic ◽  
Early Evolution ◽  
The North ◽  
Plant Group ◽  
Ecological Radiation ◽  
Origin Of Angiosperms ◽  
Crucial Test

Angiosperms are the single most important plant group in the current ecosystem. However, little is known about the origin and early evolution of angiosperms. Jurassic and earlier traces of angiosperms have been claimed multiple times from Europe and Asia, but reluctance to accept these records remains. To test the truthfulness of these claims, palaeobotanical records from continents other than Europe and Asia constitute a crucial test. Here I document a new angiosperm fruit, Dilcherifructus mexicana gen. et sp. nov, from the Middle Jurassic of Mexico. Its Jurassic age suggests that origin of angiosperms is much earlier than widely accepted, while its occurrence in the North America indicates that angiosperms were already widespread in the Jurassic, although they were still far away from their ecological radiation, which started in the Early Cretaceous.

An Archaeological Survey of Caves in Washington

1954 ◽  
Vol 19 (4) ◽  
pp. 387-389
Author(s):  
Earl Swanson ◽  
Alan Bryan
Keyword(s):  
North America ◽  
Field Work ◽  
Archaeological Research ◽  
Archaeological Survey ◽  
Large Area ◽  
Columbia Plateau ◽  
Long Period ◽  
Western Washington ◽  
The University ◽  
Private Collections

During a long period of the time when archaeological research was in progress in other areas of North America, the Columbia Plateau and western Washington lay relatively untouched and unknown. Only recently have systematic studies been undertaken by the University of Washington.The archaeological survey of cave sites in Washington, during the summer of 1952, is a part of those studies. The plan was to locate as many caves as possible, to determine if they had been occupied aboriginally, and to evaluate them with an eye to future excavation.Prior to the field work, reports had been received of caves in various parts of Washington, but the total was small, and we had little expectation of swelling the known number. Many of these had been learned of through newspaper clippings and letters, and from amateur activities. The problem, then, was not simply to examine a few choice caves for testing and excavation, but of surveying a large area in order to initiate an immediate program of excavation to save what remained. In addition to the survey of the caves, the University provided money for the examination of private collections.

scholarly journals A Balto-Scandian Middle Cambrian fauna from Peary Land, North Greenland

1988 ◽  
Vol 137 ◽  
pp. 118-118
Author(s):  
T.P Fletcher ◽  
A.K Higgins ◽  
J.S Peel
Keyword(s):  
North America ◽  
Field Work ◽  
First Record ◽  
Geological Survey ◽  
Northern Coast ◽  
Middle Cambrian ◽  
The Pacific ◽  
Cambrian Trilobite ◽  
Inland Ice ◽  
North Greenland

The first record of Middle Cambrian faunas of 'Atlantic' affinity from the Franklinian basin sequence of North Greenland was made by Poulsen (1969) who noted that previously described Greenland faunas were of 'Pacific' type. Field work by the Geological Survey of Greenland during the last decade has established that 'Atlantic' faunas are widespread in more outer shelfsequences along the northern coast of North Greenland while the 'Pacific' faunas occur within inner shelfsequences more to the south, near the margin of the Inland Ice. North Greenland preserves both faunas in dose geographical juxtaposition in only slightly tectonised geological settings. Thus, alatest Middle Cambrian trilobite fauna described by Robison (in press) from the Holm Dal Formation in an area some 40 km south of the presently discussed locality (and more inner shelf) includes a mixture of polymeroids characteristic of the Cedaria Zone of North America and agnostoids characteristic of the Lejopyge laevigata Zone of the Swedish standard zonation.

An Early Cretaceous (Berriasian) fossil-bearing locality from the Rocky Mountains of Alberta, yielding the oldest dinosaur skeletal remains from western Canada

2020 ◽  
Vol 57 (4) ◽  
pp. 542-552 ◽  
Author(s):  
Ramon S. Nagesan ◽  
James A. Campbell ◽  
Jason D. Pardo ◽  
Kendra I. Lennie ◽  
Matthew J. Vavrek ◽  
...  
Keyword(s):  
North America ◽  
Early Cretaceous ◽  
Depositional Environment ◽  
Upper Cretaceous ◽  
Upper Jurassic ◽  
High Energy ◽  
Western Canada ◽  
Western North America ◽  
Terrestrial Vertebrate ◽  
Overlying Strata

Western North America preserves iconic dinosaur faunas from the Upper Jurassic and Upper Cretaceous, but this record is interrupted by an approximately 20 Myr gap with essentially no terrestrial vertebrate fossil localities. This poorly sampled interval is nonetheless important because it is thought to include a possible mass extinction, the origin of orogenic controls on dinosaur spatial distribution, and the origin of important Upper Cretaceous dinosaur taxa. Therefore, dinosaur-bearing rocks from this interval are of particular interest to vertebrate palaeontologists. In this study, we report on one such locality from Highwood Pass, Alberta. This locality has yielded a multitaxic assemblage, with the most diagnostic material identified so far including ankylosaurian osteoderms and a turtle plastron element. The fossil horizon lies within the upper part of the Pocaterra Creek Member of the Cadomin Formation (Blairmore Group). The fossils are assigned as Berriasian (earliest Cretaceous) in age, based on previous palynomorph analyses of the Pocaterra Creek Member and underlying and overlying strata. The fossils lie within numerous cross-bedded sandstone beds separated by pebble lenses. These sediments are indicative of a relatively high-energy depositional environment, and the distribution of these fossils over multiple beds indicates that they accumulated over multiple events, possibly flash floods. The fossils exhibit a range of surface weathering, having intact to heavily weathered cortices. The presence of definitive dinosaur material from near the Jurassic–Cretaceous boundary of Alberta establishes the oldest record of dinosaur body fossils in western Canada and provides a unique opportunity to study the Early Cretaceous dinosaur faunas of western North America.

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