Metriacanthosaurid tooth from Thailand + titanosaur radius and ulna fossils from India
50 views
Skip to first unread message
Ben Creisler
Feb 3, 2026, 1:35:18 PM (9 days ago) Feb 3
to DinosaurMa...@googlegroups.com
Ben Creisler
New papers:
Samathi, S. Suteethorn & V. Suteethorn (2025) [2026]
A Metriacanthosaurid Tooth (Dinosauria: Theropoda) from the Phu Kradung Formation (Upper Jurassic–Lower Cretaceous) of Mukdahan, Thailand
Paleontological Journal 59: 776–787
doi: https://doi.org/10.1134/S0031030124601385
https://link.springer.com/article/10.1134/S0031030124601385
Metriacanthosauridae is a clade of Laurasian allosauroid theropods closely related to Allosaurus. They appeared during the Middle Jurassic to the Late Jurassic of Europe and Asia and possibly survived to the Early Cretaceous. Here, we report an isolated tooth of a theropod dinosaur from Dan Luang locality, Mukdahan Province, northeastern Thailand. The tooth is studied to establish its taxonomic affinities. A discriminant analysis and cladistic analyses of dentition-based characters and supermatrix of theropods were performed and the tooth was compared with theropod teeth from the Late Jurassic to Early Cretaceous. The analyses and synapomorphies present on the Dan Luang material indicate that the tooth can be referred to the clade Metriacanthosauridae. The synapomorphic characters present in the material include (1) asymmetric D-shaped cross-section at the crown base, (2) a longitudinal groove adjacent to the mesial carina on the lingual surface, and (3) a concave surface adjacent to the distal carina on the lingual surface. This study is the third report of metriacanthosaurids in Thailand and Southeast Asia. The result expands the distribution of this clade in the Late Jurassic–Early Cretaceous of Thailand. This study also shows that a single tooth of theropod dinosaurs has potential to offer important information that we should not overlook.
======
Samathi, S. Suteethorn & V. Suteethorn (2025) [2026]
A Metriacanthosaurid Tooth (Dinosauria: Theropoda) from the Phu Kradung Formation (Upper Jurassic–Lower Cretaceous) of Mukdahan, Thailand
Paleontological Journal 59: 776–787
doi: https://doi.org/10.1134/S0031030124601385
https://link.springer.com/article/10.1134/S0031030124601385
Metriacanthosauridae is a clade of Laurasian allosauroid theropods closely related to Allosaurus. They appeared during the Middle Jurassic to the Late Jurassic of Europe and Asia and possibly survived to the Early Cretaceous. Here, we report an isolated tooth of a theropod dinosaur from Dan Luang locality, Mukdahan Province, northeastern Thailand. The tooth is studied to establish its taxonomic affinities. A discriminant analysis and cladistic analyses of dentition-based characters and supermatrix of theropods were performed and the tooth was compared with theropod teeth from the Late Jurassic to Early Cretaceous. The analyses and synapomorphies present on the Dan Luang material indicate that the tooth can be referred to the clade Metriacanthosauridae. The synapomorphic characters present in the material include (1) asymmetric D-shaped cross-section at the crown base, (2) a longitudinal groove adjacent to the mesial carina on the lingual surface, and (3) a concave surface adjacent to the distal carina on the lingual surface. This study is the third report of metriacanthosaurids in Thailand and Southeast Asia. The result expands the distribution of this clade in the Late Jurassic–Early Cretaceous of Thailand. This study also shows that a single tooth of theropod dinosaurs has potential to offer important information that we should not overlook.
======
S. Pal & S. N. Deshmukh (2025) [2026]
Morphometric Analysis of the Distal Epiphyses of the Radius and Ulna of Titanosaurs: A Case from Central India
Paleontological Journal 59: 745–767
doi: https://doi.org/10.1134/S0031030125600015
https://link.springer.com/article/10.1134/S0031030125600015
Titanosaurs were one of the last surviving clades of sauropod dinosaurs, with a distribution that spanned the globe. India has an abundance of titanosaur fossil remains, but most of these bones are fragmented and incomplete. So far only a few radius and ulna bones of Indian titanosaurs are described, but only the ulna of Isisaurus colberti (ISIR 335/60) preserves the distal articular surface. Morphology of the distal epiphyses of the radius and ulna provides a few important characters for the phylogenetic analysis of sauropods. Here, we have described an ulna and a radius of two titanosaur specimens discovered in India. Earlier researchers have described variations in the distal articular shape for forelimb zeugopods and used them in the phylogenetic analysis of sauropods. Here, we conducted PC analyses to examine variations in the shape of the distal articular surface of radius and ulna among various taxa of eusauropods and compared them with the two specimens described here. The morphometric analysis identifies four major morphotypes in the ulnar distal articular surface shape and three major morphotypes in the radial distal articular surface shape. We also discuss evidence of homoplasy in these morphotypes among taxa from different clades of eusauropods analyzed in this study. The osteohistological study was conducted to examine bone tissue and the ontogenetic stage of these two Indian titanosaur specimens. The ulna described here belongs to a juvenile titanosaur, representing the first osteohistological description of a juvenile Indian titanosaur.
====
Morphometric Analysis of the Distal Epiphyses of the Radius and Ulna of Titanosaurs: A Case from Central India
Paleontological Journal 59: 745–767
doi: https://doi.org/10.1134/S0031030125600015
https://link.springer.com/article/10.1134/S0031030125600015
Titanosaurs were one of the last surviving clades of sauropod dinosaurs, with a distribution that spanned the globe. India has an abundance of titanosaur fossil remains, but most of these bones are fragmented and incomplete. So far only a few radius and ulna bones of Indian titanosaurs are described, but only the ulna of Isisaurus colberti (ISIR 335/60) preserves the distal articular surface. Morphology of the distal epiphyses of the radius and ulna provides a few important characters for the phylogenetic analysis of sauropods. Here, we have described an ulna and a radius of two titanosaur specimens discovered in India. Earlier researchers have described variations in the distal articular shape for forelimb zeugopods and used them in the phylogenetic analysis of sauropods. Here, we conducted PC analyses to examine variations in the shape of the distal articular surface of radius and ulna among various taxa of eusauropods and compared them with the two specimens described here. The morphometric analysis identifies four major morphotypes in the ulnar distal articular surface shape and three major morphotypes in the radial distal articular surface shape. We also discuss evidence of homoplasy in these morphotypes among taxa from different clades of eusauropods analyzed in this study. The osteohistological study was conducted to examine bone tissue and the ontogenetic stage of these two Indian titanosaur specimens. The ulna described here belongs to a juvenile titanosaur, representing the first osteohistological description of a juvenile Indian titanosaur.
====
Reply all
Reply to author
Forward
0 new messages