Post by Infinity Blade on Aug 30, 2020 5:26:14 GMT 5
Einiosaurus procurvicornis
© @ Raul Ramos->
Temporal range: Late Cretaceous; Campanian (~75.2-75.1 Ma)[1]
Scientific classification:
Life
Domain: Eukaryota
(unranked): Unikonta
(unranked): Opisthokonta
(unranked): Holozoa
(unranked): Filozoa
Kingdom: Animalia
Subkingdom: Eumetazoa
(unranked): Bilateria
Clade: Nephrozoa
Superphylum: Deuterostomia
Phylum: Chordata
Clade: Olfactores
Clade: Craniata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Clade: Eugnathostomata
Clade: Teleostomi
Clade: Tetrapoda
Clade: Reptiliomorpha
Clade: Amniota
Clade: Reptilia
Clade: Eureptilia
Clade: Romeriida
Clade: Diapsida
Clade: Neodiapsida
Clade: Archelosauria
Clade: Archosauromorpha
Clade: Archosauriformes
Clade: Crurotarsi
Clade: Archosauria
Clade: Avemetatarsalia
Clade: Ornithodira
Clade: Dinosauromorpha
Clade: Dinosauriformes
Clade: Dinosauria
Clade: †Ornithischia
Clade: †Genasauria
Clade: †Neornithischia
Clade: †Cerapoda
Clade: †Marginocephalia
Clade: †Ceratopsia
Clade: †Neoceratopsia
Clade: †Coronosauria
Superfamily: †Ceratopsoidea
Family: †Ceratopsidae
Subfamily: †Centrosaurinae
Clade: †Eucentrosaura
Tribe: †Pachyrhinosaurini
Genus: †Einiosaurus
Species: †E. procurvicornis
Einiosaurus is a genus of centrosaurine ceratopsid that lived in what is now the Two Medicine Formation of Montana[2] ~75.2-75.1 million years ago.[1] It contains only one species, E. procurvicornis.
Etymology:
Einiosaurus’ genus name is a combination of Blackfoot and Latinized Greek. ‘Eini’ is Blackfoot for buffalo, while ‘saurus’ is Latinized Greek for lizard (hence translating to “buffalo lizard”). The genus was named in honor of the Blackfoot indigenous Americans on whose land the fossils were found. The species name, “procurvicornis”, is a combination of Latin and Greek that translates to “forward-curving horn”.[3]
Description:
Einiosaurus’ most distinctive feature is its forward-curving nasal horn. This horn was long based and mediolaterally compressed. Supraorbital horns, if present, were low and rounded with convex medial surfaces. The parietal (the top of the frill) had one pair of large curved spikes projecting posteriorly (though not laterally curving like in Achelousaurus). The animal was said to be similar in morphological characters to Achelousaurus, though significantly less robust (not in postcranial characteristics, as no postcranial characters in the subfamily were identified, but in cranial characters, presumably in possessing bosses).[3]
Greg Paul has estimated Einiosaurus to be 4.5 meters long and weigh 1.3 tonnes.[4]
The distinctive skull of Einiosaurus with the forward-curving nasal horn and a total of two parietal spikes. © @ Maarten Heerlien->.
Paleobiology:
The nasal horn cores of adult Einiosaurus show osteological correlates for a cornfield sheath.[5] Although the forward-curved nasal horn is sometimes said to be a poor weapon[6], it is possible the horn was used for ramming.[5][6] Einiosaurus’ nasal horn is superficially similar to the ventrally curved horns of caprines, with the difference that it is mediolaterally compressed. The mediolaterally compressed shape may have had the effect of increasing the second moment of area of the horn core dorsoventrally, thereby increasing resistance to dorsoventral bending. Even so, the mediolaterally compressed crown of Einiosaurus’ horn is not similar to the relatively broad crowns of caprine horns. While some further testing may be needed to examine how the horn of Einiosaurus reacts to mechanical loading, the ventrally curving, ramming horns of caprines seem to be a potential analog for the horn of Einiosaurus, suggesting a use in ramming.[5] Aside from this, Greg Paul has suggested that Einiosaurus’ primary defense against tyrannosaurids was its hooked beak.[4]
According to Greg Paul, Einiosaurus inhabited seasonally dry upland woods.[4]
Evolution:
In 1992, paleontologist John R. Horner proposed that Einiosaurus, then called “Transitional taxon B”, was one of three transitional species intermediate between Campanian-aged Styracosaurus and Maastrichtian-aged Pachyrhinosaurus. According to his proposal, environmental stress from high-seaway transgressions caused habitat bottlenecking that prompted evolutionary change in multiple North American dinosaur lineages. In centrosaurine ceratopsids, this was apparently shown by a change from an upwards-pointing nasal horn (as in Styracosaurus) to a thick nasal boss (as in Pachyrhinosaurus).[7]
This proposal has not gone unchallenged, and later on Horner revised his earlier hypothesis, due to the discovery of a Pachyrhinosaurus-like centrosaurine (TMP 2002.76.1) with a nasal boss[8] that, supposedly, was at least as old as, if not older than, Rubeosaurus ovatus[9] (note that a subsequent study has found the genus name “Rubeosaurus” unnecessary[1]). However, he also noted that the close relationship between Rubeosaurus and Einiosaurus and the lack of stratigraphic overlap meant that anagenesis from the former to the latter could not be ruled out.[9]
A 2020 study was unable to reject the hypothesis that Stellasaurus (which occurs intermediate to S. albertensis and Einiosaurus) represents a transitional taxon within an anagenetic lineage of eucentrosauran centrosaurines. There is apparently no documented evidence of contemporaneous occurrences between the eucentrosaurans in question, making the opposing cladogenetic hypothesis tenuous. While the aforementioned Pachyrhinosaurus-like centrosaurine may complicate a total anagenesis scenario and may provide some support for a cladogenesis, this specimen was collected from the bottom of a deep mud-filled valley incised into the Lethbridge Coal Zone. This suggests that this specimen is actually younger than its stratigraphic position suggests, and that it may have been penecomtemporaneous with Achelousaurus. Therefore, Einiosaurus may indeed represent a transitional form intermediate between centrosaurines possessing an upwards-pointing nasal horn and centrosaurines possessing bosses.[1] The change in horn morphology over time within this centrosaurine lineage represents a trend in increasing intensity in agonistic behaviors, from horn clashing (basal centrosaurines had longer supraorbital horns) to high-energy headbutting.[5]
Fig. 11 of [1]. Stratigraphic and temporal relationships of different centrosaurine taxa as part of an anagenetic lineage. (a) is Styracosaurus albertensis, (b) is Stellasaurus ancellae, (c) and (c’) are both Einiosaurus procurvicornis, (d) is Achelousaurus horneri, and (e) is Pachyrhinosaurus lakustai.
References:
[1] Wilson, J. P., Ryan, M. J., & Evans, D. C. (2020). A new, transitional centrosaurine ceratopsid from the Upper Cretaceous Two Medicine Formation of Montana and the evolution of the ‘Styracosaurus-line’dinosaurs. Royal Society Open Science, 7(4), 200284.
[2] paleobiodb.org/classic/basicTaxonInfo?taxon_no=53952
[3] Sampson, S. D. (1995). Two new horned dinosaurs from the Upper Cretaceous Two Medicine Formation of Montana; with a phylogenetic analysis of the Centrosaurinae (Ornithischia: Ceratopsidae). Journal of Vertebrate Paleontology, 15(4), 743-760.
[4] Paul, G. S. (2016). The Princeton field guide to dinosaurs (Vol. 110). Princeton University Press.
[5] Hieronymus, T. L., Witmer, L. M., Tanke, D. H., & Currie, P. J. (2009). The facial integument of centrosaurine ceratopsids: morphological and histological correlates of novel skin structures. The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology: Advances in Integrative Anatomy and Evolutionary Biology, 292(9), 1370-1396.
[6] Dodson, P. (2017). The Horned Dinosaurs: A Natural History (Vol. 4834). Princeton University Press. p. 19
[7] Horner, J. R., Varricchio, D. J., & Goodwin, M. B. (1992). Marine transgressions and the evolution of Cretaceous dinosaurs. Nature, 358(6381), 59-61.
[8] Ryan, M. J., Eberth, D. A., Brinkman, D. B., Currie, P. J., & Tanke, D. H. (2010). A new Pachyrhinosaurus-like ceratopsid from the upper Dinosaur Park Formation (late Campanian) of southern Alberta, Canada. New perspectives on horned dinosaurs. Edited by MJ Ryan, BJ Chinnery-Allgeier, and DA Eberth. Indiana University Press, Bloomington, IN, 141-155.
[9] McDonald, A. T., & Horner, J. R. (2010). New material of “Styracosaurus” ovatus from the Two Medicine Formation of Montana. New Perspectives on Horned Dinosaurs, 156-168.
© @ Raul Ramos->
Temporal range: Late Cretaceous; Campanian (~75.2-75.1 Ma)[1]
Scientific classification:
Life
Domain: Eukaryota
(unranked): Unikonta
(unranked): Opisthokonta
(unranked): Holozoa
(unranked): Filozoa
Kingdom: Animalia
Subkingdom: Eumetazoa
(unranked): Bilateria
Clade: Nephrozoa
Superphylum: Deuterostomia
Phylum: Chordata
Clade: Olfactores
Clade: Craniata
Subphylum: Vertebrata
Infraphylum: Gnathostomata
Clade: Eugnathostomata
Clade: Teleostomi
Clade: Tetrapoda
Clade: Reptiliomorpha
Clade: Amniota
Clade: Reptilia
Clade: Eureptilia
Clade: Romeriida
Clade: Diapsida
Clade: Neodiapsida
Clade: Archelosauria
Clade: Archosauromorpha
Clade: Archosauriformes
Clade: Crurotarsi
Clade: Archosauria
Clade: Avemetatarsalia
Clade: Ornithodira
Clade: Dinosauromorpha
Clade: Dinosauriformes
Clade: Dinosauria
Clade: †Ornithischia
Clade: †Genasauria
Clade: †Neornithischia
Clade: †Cerapoda
Clade: †Marginocephalia
Clade: †Ceratopsia
Clade: †Neoceratopsia
Clade: †Coronosauria
Superfamily: †Ceratopsoidea
Family: †Ceratopsidae
Subfamily: †Centrosaurinae
Clade: †Eucentrosaura
Tribe: †Pachyrhinosaurini
Genus: †Einiosaurus
Species: †E. procurvicornis
Einiosaurus is a genus of centrosaurine ceratopsid that lived in what is now the Two Medicine Formation of Montana[2] ~75.2-75.1 million years ago.[1] It contains only one species, E. procurvicornis.
Etymology:
Einiosaurus’ genus name is a combination of Blackfoot and Latinized Greek. ‘Eini’ is Blackfoot for buffalo, while ‘saurus’ is Latinized Greek for lizard (hence translating to “buffalo lizard”). The genus was named in honor of the Blackfoot indigenous Americans on whose land the fossils were found. The species name, “procurvicornis”, is a combination of Latin and Greek that translates to “forward-curving horn”.[3]
Description:
Einiosaurus’ most distinctive feature is its forward-curving nasal horn. This horn was long based and mediolaterally compressed. Supraorbital horns, if present, were low and rounded with convex medial surfaces. The parietal (the top of the frill) had one pair of large curved spikes projecting posteriorly (though not laterally curving like in Achelousaurus). The animal was said to be similar in morphological characters to Achelousaurus, though significantly less robust (not in postcranial characteristics, as no postcranial characters in the subfamily were identified, but in cranial characters, presumably in possessing bosses).[3]
Greg Paul has estimated Einiosaurus to be 4.5 meters long and weigh 1.3 tonnes.[4]
The distinctive skull of Einiosaurus with the forward-curving nasal horn and a total of two parietal spikes. © @ Maarten Heerlien->.
Paleobiology:
The nasal horn cores of adult Einiosaurus show osteological correlates for a cornfield sheath.[5] Although the forward-curved nasal horn is sometimes said to be a poor weapon[6], it is possible the horn was used for ramming.[5][6] Einiosaurus’ nasal horn is superficially similar to the ventrally curved horns of caprines, with the difference that it is mediolaterally compressed. The mediolaterally compressed shape may have had the effect of increasing the second moment of area of the horn core dorsoventrally, thereby increasing resistance to dorsoventral bending. Even so, the mediolaterally compressed crown of Einiosaurus’ horn is not similar to the relatively broad crowns of caprine horns. While some further testing may be needed to examine how the horn of Einiosaurus reacts to mechanical loading, the ventrally curving, ramming horns of caprines seem to be a potential analog for the horn of Einiosaurus, suggesting a use in ramming.[5] Aside from this, Greg Paul has suggested that Einiosaurus’ primary defense against tyrannosaurids was its hooked beak.[4]
According to Greg Paul, Einiosaurus inhabited seasonally dry upland woods.[4]
Evolution:
In 1992, paleontologist John R. Horner proposed that Einiosaurus, then called “Transitional taxon B”, was one of three transitional species intermediate between Campanian-aged Styracosaurus and Maastrichtian-aged Pachyrhinosaurus. According to his proposal, environmental stress from high-seaway transgressions caused habitat bottlenecking that prompted evolutionary change in multiple North American dinosaur lineages. In centrosaurine ceratopsids, this was apparently shown by a change from an upwards-pointing nasal horn (as in Styracosaurus) to a thick nasal boss (as in Pachyrhinosaurus).[7]
This proposal has not gone unchallenged, and later on Horner revised his earlier hypothesis, due to the discovery of a Pachyrhinosaurus-like centrosaurine (TMP 2002.76.1) with a nasal boss[8] that, supposedly, was at least as old as, if not older than, Rubeosaurus ovatus[9] (note that a subsequent study has found the genus name “Rubeosaurus” unnecessary[1]). However, he also noted that the close relationship between Rubeosaurus and Einiosaurus and the lack of stratigraphic overlap meant that anagenesis from the former to the latter could not be ruled out.[9]
A 2020 study was unable to reject the hypothesis that Stellasaurus (which occurs intermediate to S. albertensis and Einiosaurus) represents a transitional taxon within an anagenetic lineage of eucentrosauran centrosaurines. There is apparently no documented evidence of contemporaneous occurrences between the eucentrosaurans in question, making the opposing cladogenetic hypothesis tenuous. While the aforementioned Pachyrhinosaurus-like centrosaurine may complicate a total anagenesis scenario and may provide some support for a cladogenesis, this specimen was collected from the bottom of a deep mud-filled valley incised into the Lethbridge Coal Zone. This suggests that this specimen is actually younger than its stratigraphic position suggests, and that it may have been penecomtemporaneous with Achelousaurus. Therefore, Einiosaurus may indeed represent a transitional form intermediate between centrosaurines possessing an upwards-pointing nasal horn and centrosaurines possessing bosses.[1] The change in horn morphology over time within this centrosaurine lineage represents a trend in increasing intensity in agonistic behaviors, from horn clashing (basal centrosaurines had longer supraorbital horns) to high-energy headbutting.[5]
Fig. 11 of [1]. Stratigraphic and temporal relationships of different centrosaurine taxa as part of an anagenetic lineage. (a) is Styracosaurus albertensis, (b) is Stellasaurus ancellae, (c) and (c’) are both Einiosaurus procurvicornis, (d) is Achelousaurus horneri, and (e) is Pachyrhinosaurus lakustai.
References:
[1] Wilson, J. P., Ryan, M. J., & Evans, D. C. (2020). A new, transitional centrosaurine ceratopsid from the Upper Cretaceous Two Medicine Formation of Montana and the evolution of the ‘Styracosaurus-line’dinosaurs. Royal Society Open Science, 7(4), 200284.
[2] paleobiodb.org/classic/basicTaxonInfo?taxon_no=53952
[3] Sampson, S. D. (1995). Two new horned dinosaurs from the Upper Cretaceous Two Medicine Formation of Montana; with a phylogenetic analysis of the Centrosaurinae (Ornithischia: Ceratopsidae). Journal of Vertebrate Paleontology, 15(4), 743-760.
[4] Paul, G. S. (2016). The Princeton field guide to dinosaurs (Vol. 110). Princeton University Press.
[5] Hieronymus, T. L., Witmer, L. M., Tanke, D. H., & Currie, P. J. (2009). The facial integument of centrosaurine ceratopsids: morphological and histological correlates of novel skin structures. The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology: Advances in Integrative Anatomy and Evolutionary Biology, 292(9), 1370-1396.
[6] Dodson, P. (2017). The Horned Dinosaurs: A Natural History (Vol. 4834). Princeton University Press. p. 19
[7] Horner, J. R., Varricchio, D. J., & Goodwin, M. B. (1992). Marine transgressions and the evolution of Cretaceous dinosaurs. Nature, 358(6381), 59-61.
[8] Ryan, M. J., Eberth, D. A., Brinkman, D. B., Currie, P. J., & Tanke, D. H. (2010). A new Pachyrhinosaurus-like ceratopsid from the upper Dinosaur Park Formation (late Campanian) of southern Alberta, Canada. New perspectives on horned dinosaurs. Edited by MJ Ryan, BJ Chinnery-Allgeier, and DA Eberth. Indiana University Press, Bloomington, IN, 141-155.
[9] McDonald, A. T., & Horner, J. R. (2010). New material of “Styracosaurus” ovatus from the Two Medicine Formation of Montana. New Perspectives on Horned Dinosaurs, 156-168.
