scholarly journals Osteology ofGaleamopus pabstisp. nov. (Sauropoda: Diplodocidae), with implications for neurocentral closure timing, and the cervico-dorsal transition in diplodocids

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e3179 ◽  
Author(s):  
Emanuel Tschopp ◽  
Octávio Mateus
Keyword(s):  
Cervical Vertebrae ◽  
Niche Partitioning ◽  
Type Specimen ◽  
Upper Jurassic ◽  
Body Parts ◽  
Morrison Formation ◽  
Dorsal Vertebra ◽  
Important Indicator ◽  
Horizontal Canal ◽  
Holotype Specimen

Diplodocids are among the best known sauropod dinosaurs. Numerous specimens of currently 15 accepted species belonging to ten genera have been reported from the Late Jurassic to Early Cretaceous of North and South America, Europe, and Africa. The highest diversity is known from the Upper Jurassic Morrison Formation of the western United States: a recent review recognized 12 valid, named species, and possibly three additional, yet unnamed ones. One of these is herein described in detail and referred to the genusGaleamopus. The holotype specimen ofGaleamopus pabstisp. nov., SMA 0011, is represented by material from all body parts but the tail, and was found at the Howe-Scott Quarry in the northern Bighorn Basin in Wyoming, USA. Autapomorphic features of the new species include a horizontal canal on the maxilla that connects the posterior margin of the preantorbital and the ventral margin of the antorbital fenestrae, a vertical midline groove marking the sagittal nuchal crest, the presence of a large foramen connecting the postzygapophyseal centrodiapophyseal fossa and the spinopostzygapophyseal fossa of mid- and posterior cervical vertebrae, a very robust humerus, a laterally placed, rugose tubercle on the concave proximal portion of the anterior surface of the humerus, a relatively stout radius, the absence of a distinct ambiens process on the pubis, and a distinctly concave posteroventral margin of the ascending process of the astragalus. In addition to the holotype specimen SMA 0011, the skull USNM 2673 can also be referred toGaleamopus pabsti. Histology shows that the type specimen SMA 0011 is sexually mature, although neurocentral closure was not completed at the time of death. Because SMA 0011 has highly pneumatized cervical vertebrae, the development of the lamination appears a more important indicator for individual age than neurocentral fusion patterns. SMA 0011 is one of very few sauropod specimens that preserves the cervico-dorsal transition in both vertebrae and ribs. The association of ribs with their respective vertebrae shows that the transition between cervical and dorsal vertebrae is significantly different inGaleamopus pabstithan inDiplodocus carnegiiorApatosaurus louisae, being represented by a considerable shortening of the centra from the last cervical to the first dorsal vertebra. Diplodocids show a surprisingly high diversity in the Morrison Formation. This can possibly be explained by a combination of geographical and temporal segregation, and niche partitioning.

scholarly journals Morphological variation in Naomichelys (Testudinata: Solemydidae): insights from a new specimen from the Lower Cretaceous Cloverly Formation of Montana

2015 ◽  
Author(s):  
Daniel Lawver
Keyword(s):  
North America ◽  
Morphological Variation ◽  
Lower Cretaceous ◽  
Cervical Vertebrae ◽  
Shoulder Girdle ◽  
Distinct Species ◽  
Upper Jurassic ◽  
Holotype Specimen ◽  
Surface Ornamentation ◽  
The Right

Background. Solemydidae is an enigmatic clade of stem turtles, which is primarily represented by fragmentary shell material found in Upper Jurassic and Cretaceous deposits of Europe and North America. Specimens are typically identified by a distinct surface ornamentation comprised of tall, narrow tubercles, which are often incompletely preserved due to taphonomic processes. The only currently recognized North American species of Solemydidae, Naomichelys speciosa was erected in 1908 on the basis of a nearly complete entoplastron from the Lower Cretaceous Cloverly Formation of Montana; however, a far more complete specimen from the Lower Cretaceous Antler Formation of Texas (FMNH PR273) was recently referred to this species and has shed light on the morphology of Naomichelys. Here, I describe a partial skeleton (MOR 941) that was discovered in 1995 near the type locality in Montana, which allows for the first look at variation in many of the skeletal elements of the genus. Methods. Morphological variation of Naomichelys was determined by comparison of MOR 941 to the holotype specimen and FMNH PR273 from the literature. Results. MOR 941 is referable to Solemydidae based on a large, diamond shaped entoplastron, which exhibits the distinctive solemydid surface ornamentation and an entoplastral scute, and is referable to Naomichelys because of its near identical morphology to that of the holotype. This specimen consists of the carapace, plastron, four cervical vertebrae, both shoulder girdles, and the right femur. Preserved carapacial elements are the right costals and peripherals in articulation, albeit somewhat crushed, disarticulated left costals, and a single neural. Using peripheral and costal sutures as well as marginal sulci as landmarks, peripherals 1 – 4 are identified, which indicates that the nuchal notch is either reduced or lacking completely. The plastron is well preserved with only portions of the left bridge and xiphiplastra missing and a central plastral fontanel is completely lacking. Cervical vertebrae 5 – 8 are preserved and show varying states of completeness with C7 being the most complete. Cervical 5 preserves a ventral keel on the centrum that is well developed and projects well beyond the central articulations. The shoulder girdle elements are similar to FMNH PR273 but are less well preserved and are not sutured together. The femur is complete and almost identical to FMNH PR273; however, the distal condyles are equally developed. Discussion. The morphological differences between MOR 941 and the Texas material suggest two plausible conclusions. 1) They demonstrate two different ontogenetic stages of development, with MOR 941 representing a skeletally more mature, albeit smaller individual; or 2) there are two distinct species of Naomichelys from the Lower Cretaceous of North America.

scholarly journals The neck of Barosaurus was not only longer but also wider than those of Diplodocus and other diplodocines

2013 ◽  
Author(s):  
Michael P Taylor ◽  
Mathew J Wedel
Keyword(s):  
United States ◽  
Cervical Vertebrae ◽  
Ground Level ◽  
Upper Jurassic ◽  
Western United States ◽  
Morrison Formation ◽  
Feeding Style ◽  
Functional Complex ◽  
Characteristic Features

Barosaurus is a diplodocid sauropod from the Upper Jurassic Morrison Formation of the western United States, and is known for its very long neck. It is related to the sympatric Diplodocus, and often thought of as more or less identical except with a longer neck. The holotype YPM 429 includes three and a half posterior cervical vertebrae, somewhat distorted and damaged, which are nevertheless very distinctive and quite different from those of Diplodocus. The cervicals of the better known and more complete referred Barosaurus specimen AMNH 6341 show the same characteristic features as the holotype, though not to the same extent: transversely broad but anteroposteriorly short zygapophyseal facets; prezygapophyses carried on broad, squared-off rami; zygapophyses shifted forward relative to the centrum; diapophyses, parapophyses and neural spines shifted backwards; and broad diapophyseal “wings”. These features form a single functional complex, enabling great lateral flexibility, but restricting vertical flexibility. This may indicate that Barosaurus used a different feeding style from other sauropods perhaps sweeping out long arcs at ground level. The Morrison Formation contains at least nine diplodocid species in six to eight genera whose relationships are not yet fully understood, but Barosaurus remains distinct from its relatives.

scholarly journals Morphological variation in Naomichelys (Testudinata: Solemydidae): insights from a new specimen from the Lower Cretaceous Cloverly Formation of Montana

2015 ◽  
Author(s):  
Daniel Lawver
Keyword(s):  
North America ◽  
Morphological Variation ◽  
Lower Cretaceous ◽  
Cervical Vertebrae ◽  
Shoulder Girdle ◽  
Distinct Species ◽  
Upper Jurassic ◽  
Holotype Specimen ◽  
Surface Ornamentation ◽  
The Right

Background. Solemydidae is an enigmatic clade of stem turtles, which is primarily represented by fragmentary shell material found in Upper Jurassic and Cretaceous deposits of Europe and North America. Specimens are typically identified by a distinct surface ornamentation comprised of tall, narrow tubercles, which are often incompletely preserved due to taphonomic processes. The only currently recognized North American species of Solemydidae, Naomichelys speciosa was erected in 1908 on the basis of a nearly complete entoplastron from the Lower Cretaceous Cloverly Formation of Montana; however, a far more complete specimen from the Lower Cretaceous Antler Formation of Texas (FMNH PR273) was recently referred to this species and has shed light on the morphology of Naomichelys. Here, I describe a partial skeleton (MOR 941) that was discovered in 1995 near the type locality in Montana, which allows for the first look at variation in many of the skeletal elements of the genus. Methods. Morphological variation of Naomichelys was determined by comparison of MOR 941 to the holotype specimen and FMNH PR273 from the literature. Results. MOR 941 is referable to Solemydidae based on a large, diamond shaped entoplastron, which exhibits the distinctive solemydid surface ornamentation and an entoplastral scute, and is referable to Naomichelys because of its near identical morphology to that of the holotype. This specimen consists of the carapace, plastron, four cervical vertebrae, both shoulder girdles, and the right femur. Preserved carapacial elements are the right costals and peripherals in articulation, albeit somewhat crushed, disarticulated left costals, and a single neural. Using peripheral and costal sutures as well as marginal sulci as landmarks, peripherals 1 – 4 are identified, which indicates that the nuchal notch is either reduced or lacking completely. The plastron is well preserved with only portions of the left bridge and xiphiplastra missing and a central plastral fontanel is completely lacking. Cervical vertebrae 5 – 8 are preserved and show varying states of completeness with C7 being the most complete. Cervical 5 preserves a ventral keel on the centrum that is well developed and projects well beyond the central articulations. The shoulder girdle elements are similar to FMNH PR273 but are less well preserved and are not sutured together. The femur is complete and almost identical to FMNH PR273; however, the distal condyles are equally developed. Discussion. The morphological differences between MOR 941 and the Texas material suggest two plausible conclusions. 1) They demonstrate two different ontogenetic stages of development, with MOR 941 representing a skeletally more mature, albeit smaller individual; or 2) there are two distinct species of Naomichelys from the Lower Cretaceous of North America.

scholarly journals The neck of Barosaurus: longer, wider and weirder than those of Diplodocus and other diplodocines

2016 ◽  
Author(s):  
Michael P Taylor ◽  
Mathew J Wedel
Keyword(s):  
United States ◽  
Cervical Vertebrae ◽  
Ground Level ◽  
Upper Jurassic ◽  
Western United States ◽  
Morrison Formation ◽  
Feeding Style ◽  
Functional Complex ◽  
Characteristic Features

Barosaurus is a diplodocid sauropod from the Upper Jurassic Morrison Formation of the western United States, and is known for its very long neck. It is closely related to the sympatric Diplodocus, and often thought of as more or less identical except with a longer neck. The holotype YPM 429 includes three and a half posterior cervical vertebrae, somewhat distorted and damaged, which are nevertheless very distinctive and quite different from those of Diplodocus. The cervicals of the better known and more complete referred Barosaurus specimen AMNH 6341 show the same characteristic features as the holotype, though not to the same extent: transversely broad but anteroposteriorly short zygapophyseal facets; prezygapophyses carried on broad, squared-off rami; zygapophyses shifted forward relative to the centrum; diapophyses, parapophyses and neural spines shifted backwards; and broad diapophyseal “wings”. These features form a single functional complex, enabling great lateral flexibility, but restricting vertical flexibility. This may indicate that Barosaurus used a different feeding style from other sauropods perhaps sweeping out long arcs at ground level. The Morrison Formation contains at least nine diplodocid species in six to eight genera whose relationships are not yet fully understood, but Barosaurus remains distinct from its relatives.

scholarly journals Maraapunisaurus fragillimus, N.G. (formerly Amphicoelias fragillimus), a basal Rebbachisaurid from the Morrison Formation (Upper Jurassic) of Colorado

2018 ◽  
Vol 5 ◽  
pp. 227-244 ◽  
Author(s):  
Ken Carpenter
Keyword(s):  
Tail Length ◽  
Upper Jurassic ◽  
Natural Sciences ◽  
Neural Spine ◽  
Morrison Formation ◽  
Original Publication ◽  
Dorsal Vertebra ◽  
Academy Of Natural Sciences

In 1878, Oramel Lucas shipped to E.D. Cope of the Academy of Natural Sciences of Philadelphia, a huge 1.5-m-tall neural spine from the dorsal vertebra of a sauropod (from the Upper Jurassic Morrison Formation) that Cope named and illustrated as Amphicoelis fragillimus.The holotype was lost and all that is known of the specimen is from Cope's original publication. Reanalysis of Cope's publication in light of other sauropods discovered since 1878 indicates that Amphicoelias fragillimus is a basal rebbachisaurid characterized by pneumatic neural spine and arch, and the unambiguous rebbachisaurid character of a festooned spinodiapophyseallamina. Because the specimen can no longer be referred to the basal diplodo­ coid Amphicoelias, the genus name is replaced with Maraapunisaurus n.g. As a rebbachisaurid, revised dimensions indicate a dorsal vertebra 2.4 m tall and a head-to-tail length for the animal of30.3 to 32m, significantly less than previous estimates.

scholarly journals Maraapunisaurus fragillimus, N.G. (formerly Amphicoelias fragillimus), a basal Rebbachisaurid from the Morrison Formation (Upper Jurassic) of Colorado

2018 ◽  
Vol 5 ◽  
pp. 227-244 ◽  
Author(s):  
Kenneth Carpenter
Keyword(s):  
Tail Length ◽  
Upper Jurassic ◽  
Natural Sciences ◽  
Neural Spine ◽  
Morrison Formation ◽  
Original Publication ◽  
Dorsal Vertebra ◽  
Academy Of Natural Sciences

In 1878, Oramel Lucas shipped to E.D. Cope of the Academy of Natural Sciences of Philadelphia, a huge 1.5-m-tall neural spine from the dorsal vertebra of a sauropod (from the Upper Jurassic Morrison Formation) that Cope named and illustrated as Amphicoelis fragillimus.The holotype was lost and all that is known of the specimen is from Cope's original publication. Reanalysis of Cope's publication in light of other sauropods discovered since 1878 indicates that Amphicoelias fragillimus is a basal rebbachisaurid characterized by pneumatic neural spine and arch, and the unambiguous rebbachisaurid character of a festooned spinodiapophyseallamina. Because the specimen can no longer be referred to the basal diplodo­ coid Amphicoelias, the genus name is replaced with Maraapunisaurus n.g. As a rebbachisaurid, revised dimensions indicate a dorsal vertebra 2.4 m tall and a head-to-tail length for the animal of 30.3 to 32m, significantly less than previous estimates.

scholarly journals The neck of Barosaurus: longer, wider and weirder than those of Diplodocus and other diplodocines

2016 ◽  
Author(s):  
Michael P Taylor ◽  
Mathew J Wedel
Keyword(s):  
United States ◽  
Cervical Vertebrae ◽  
Ground Level ◽  
Upper Jurassic ◽  
Western United States ◽  
Morrison Formation ◽  
Feeding Style ◽  
Functional Complex ◽  
Characteristic Features

Barosaurus is a diplodocid sauropod from the Upper Jurassic Morrison Formation of the western United States, and is known for its very long neck. It is closely related to the sympatric Diplodocus, and often thought of as more or less identical except with a longer neck. The holotype YPM 429 includes three and a half posterior cervical vertebrae, somewhat distorted and damaged, which are nevertheless very distinctive and quite different from those of Diplodocus. The cervicals of the better known and more complete referred Barosaurus specimen AMNH 6341 show the same characteristic features as the holotype, though not to the same extent: transversely broad but anteroposteriorly short zygapophyseal facets; prezygapophyses carried on broad, squared-off rami; zygapophyses shifted forward relative to the centrum; diapophyses, parapophyses and neural spines shifted backwards; and broad diapophyseal “wings”. These features form a single functional complex, enabling great lateral flexibility, but restricting vertical flexibility. This may indicate that Barosaurus used a different feeding style from other sauropods perhaps sweeping out long arcs at ground level. The Morrison Formation contains at least nine diplodocid species in six to eight genera whose relationships are not yet fully understood, but Barosaurus remains distinct from its relatives.

scholarly journals Evidence for niche partitioning among ground-height browsing sauropods from the Upper Jurassic Morrison Formation of North America

2018 ◽  
Vol 5 ◽  
pp. 95-103 ◽  
Author(s):  
Julia McHugh
Keyword(s):  
Computed Tomography ◽  
North America ◽  
Late Jurassic ◽  
Feeding Strategy ◽  
Niche Partitioning ◽  
Upper Jurassic ◽  
Ct Scans ◽  
Close Relative ◽  
Morrison Formation ◽  
High Count

Two tooth-bearing snout fragments from a diplodocid sauropod from the Brushy Basin Member of the Morrison Formation (Upper Jurassic) excavated from the Mygatt-Moore Quarry in Rabbit Valley, Colora­do are described. The Mygatt-Moore Quarry has produced thousands of vertebrate fossils from the Brushy Basin Member, with the diplodocid Apatosaurus cf. louisae and the tetanuran Allosaurus fragilis dominat­ing the assemblage. Additionally, remains of another diplodocid, Diplodocus sp., have been found near the quarry within Rabbit Valley. Both specimens in this study preserve eight teeth per alveolar position, as observed through broken surfaces at the gross anatomical level and also through computed tomography (CT) scans. This is inconsistent with the genus Diplodocus sp., which has been previously shown to have a maximum of six teeth per alveolus. The presence of eight replacement teeth per alveolus has previously only been reported in the Cretaceous rebbachisaurid Nigersaurus taqueti, which has been interpreted to have occupied a similar ground-height browsing feeding strategy to both Diplodocus and Apatosaurus. This is the first report of this type of high-count replacement teeth in a diplodocid sauropod from the Morrison Formation. The high number of replacement teeth in a close relative to the contemporaneous Diplodocus provides evidence for niche partitioning among the contemporary ground-height browsing diplodocid sauropods of the Late Jurassic Period in North America.

scholarly journals Evidence for niche partitioning among ground-height browsing sauropods from the Upper Jurassic Morrison Formation of North America

2018 ◽  
Vol 5 ◽  
pp. 95-103 ◽  
Author(s):  
Julia B. McHugh
Keyword(s):  
Computed Tomography ◽  
North America ◽  
Late Jurassic ◽  
Feeding Strategy ◽  
Niche Partitioning ◽  
Upper Jurassic ◽  
Ct Scans ◽  
Close Relative ◽  
Morrison Formation ◽  
High Count

Two tooth-bearing snout fragments from a diplodocid sauropod from the Brushy Basin Member of the Morrison Formation (Upper Jurassic) excavated from the Mygatt-Moore Quarry in Rabbit Valley, Colora­do are described. The Mygatt-Moore Quarry has produced thousands of vertebrate fossils from the Brushy Basin Member, with the diplodocid Apatosaurus cf. louisae and the tetanuran Allosaurus fragilis dominat­ing the assemblage. Additionally, remains of another diplodocid, Diplodocus sp., have been found near the quarry within Rabbit Valley. Both specimens in this study preserve eight teeth per alveolar position, as observed through broken surfaces at the gross anatomical level and also through computed tomography (CT) scans. This is inconsistent with the genus Diplodocus sp., which has been previously shown to have a maximum of six teeth per alveolus. The presence of eight replacement teeth per alveolus has previously only been reported in the Cretaceous rebbachisaurid Nigersaurus taqueti, which has been interpreted to have occupied a similar ground-height browsing feeding strategy to both Diplodocus and Apatosaurus. This is the first report of this type of high-count replacement teeth in a diplodocid sauropod from the Morrison Formation. The high number of replacement teeth in a close relative to the contemporaneous Diplodocus provides evidence for niche partitioning among the contemporary ground-height browsing diplodocid sauropods of the Late Jurassic Period in North America.

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