Dicraeosauridae

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Dicraeosaurids
Temporal range: Middle Jurassic - Early Cretaceous,
166–122  Ma
Dino amargasaurus.jpg
Amargasaurus
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade: Saurischia
Clade: Sauropodomorpha
Clade: Sauropoda
Superfamily: Diplodocoidea
Clade: Flagellicaudata
Family: Dicraeosauridae
Janensch, 1929
Genera

Dicraeosauridae is a family of diplodocoid sauropods who are the sister group to Diplodocidae. Dicraeosaurids are a part of the Flagellicaudata, along with Diplodocidae. Dicraeosauridae includes genera such as Amargasaurus , Suuwassea , Dicraeosaurus , and Brachytrachelopan . Specimens of this family have been found in North America, Asia, Africa, and South America. [1] In 2023, a dicraeosaurid fossil was discovered in India for the first time. [2] Their temporal range is from the Early or Middle Jurassic to the Early Cretaceous. [3] [4] [5] Few dicraeosaurids survived into the Cretaceous, the youngest of which was Amargasaurus . [6]

Contents

The group was first described by German paleontologist Werner Janensch in 1914 with the discovery of Dicraeosaurus in Tanzania. [7] Dicraeosauridae are distinct from other sauropods because of their relatively short neck size and small body size. [3]

The clade is monophyletic and well-supported phylogenetically with thirteen unambiguous synapomorphies uniting it. [6] They diverged from Diplodocidae in the Mid-Jurassic, as evidenced by the diversity of dicraeosaurids in both South America and East Africa when Gondwana was still united by land. [6] However, there is some disagreement among paleontologists on the phylogenetic placement of Suuwassea , the only genus of the Dicraeosauridae to be found in North America. It has been characterized as a basal dicraeosaurid by some and a member of the Diplodocidae by others. [6] [8] The placement of Suuwassea within Dicraeosauridae or Diplodocidae has substantial biogeographic implications for the evolution of Dicraeosauridae. [9]

Classification

Dicraeosaurids, drawn to scale. Dicraeosaurids BW.png
Dicraeosaurids, drawn to scale.

Dicraeosaurids are a part of Diplodocoidea and are the sister group to Diploidocidae. In the past two decades, the known diversity of the group has doubled. [6] However, the classification of Suuwassea as a dicraeosaurid is not universally agreed upon. [6] [8] Some phylogenetic analyses have found Suuwassea to be a basal diplodocoid instead of a dicraeosaurid. [8] One 2015 analysis has even found Dyslocosaurus as a member of Dicraeosauridae. [10] A 2016 reappraisal of Amargatitanis has placed it into the Dicraeosauridae, as well. [11] In 2018 a new genus, Pilmatueia , was described. [12]

Size comparison of the most complete members of the sauropod family Dicraeosauridae Dicraeosauridae Scale.svg
Size comparison of the most complete members of the sauropod family Dicraeosauridae

Dicraeosaurids are differentiated from their sister group, diplodocids, and from most sauropods by their relatively small body size and short necks. [13] Dicraeosaurids are advanced sauropods within the monophyletic clade Neosauropoda, which is generally characterized by gigantism. The relatively small body size of dicraeosaurids make them an important outlier relative to other taxa in Neosauropoda. [14]

Phylogeny

There have been several different proposed phylogenies of Dicraeosauridae and the intra-group cladistics are not resolved. Suuwassea is variably positioned as either a basal dicraeosaurid or a basal diplodocoid. The phylogeny published by Tschopp and colleagues in 2015 is as follows: [10]

Tschopp includes Dyslocosaurus and Dystrophaeus as dicraeosaurids, two genera traditionally not considered to be part of Dicraeosauridae. The specimens of Dystrophaeus viamelae are highly fragmentary, with only a few bones available for study including an ulna, partial scapula, partial dorsal vertebrae, a distal radius, and some metacarpals. Dyslocosaurus polyonychius also has extremely limited fossil evidence that only includes appendicular elements, and the position of it in Tschopp's phylogeny is therefore considered "preliminary". [10]

Several studies, however, do not include even Suuwassea in Dicraeosauridae, such as Sereno et al. (2007); [13] and JD Harris (2006). [9] Other studies, however, recover Suuwassea as a basal dicraeosaurid, including Whitlock (2010) [6] and Salgado et al. (2006). [15]

Paleobiology

Feeding behavior

As sauropods, dicraeosaurids are obligate herbivores. Due to their relatively small necks and skull shape, it has been deduced that dicraeosaurids and diplodocids primarily browsed close to the ground or at mid height. [6] [13] Among the dicraeosaurids, only Dicraeosaurus has well-preserved dentition. This makes it difficult for paleontologists to make definitive statements about Dicraeosauridae feeding behavior compared to diplodocid feeding behavior. [16] However, compared to its known relatives, Dicraeosaurus is unique in that it has an equal number of teeth in the upper and lower jaw, though teeth in the lower jaw are replaced more slowly. [16]

Anatomy

Dicraeosaurids are characterized by their relatively small body size, short necks, and long neural spines. [17] They are 10–13 meters in body length. [17] They share thirteen unambiguous synapomorphies including dorsal vertebrae without pleurocoels, the presence of a ventrally directed prong on the squamosal, and a subtriangular-shaped dentary symphysis. [6]

Distribution and evolution

Early Dicraeosaurid specimens have been found in three continents - Africa, South America, and North America. The distribution of species is primarily Gondwonan, with the exception of the North American Suuwassea. The presence of Suuwassea in North America is unique among dicraeosaurids, therefore making the proper taxonomic classification of Suuwassea essential. The group likely first diverged from the diplodocids in the middle Jurassic in North America and subsequently dispersed into Gondwana, with the most diversity in East Africa and South America. [6] Amargasaurus was the latest surviving dicraeosaurid genus, living into the Early Cretaceous period. [6]

Recently from the Thar Desert, a dicraeosaurid fossil dating back to 167 million years ago was discovered in 2023. This present-day sweltering expanse of India was a lush green tropical coastline that bordered the Tethys Ocean, serving as a habitat for a diverse range of dinosaurs during the Mesozoic Era. This discovery marks the first of its kind to be unearthed in Asian continent and is also the oldest specimen ever recorded in the global fossil record. [2]

Sources

  1. Gallina, Pablo A.; Apesteguía, Sebastián; Haluza, Alejandro; Canale, Juan I. (2014-05-14). "A Diplodocid Sauropod Survivor from the Early Cretaceous of South America". PLOS ONE. 9 (5): e97128. Bibcode:2014PLoSO...997128G. doi: 10.1371/journal.pone.0097128 . ISSN   1932-6203. PMC   4020797 . PMID   24828328.
  2. 1 2 "The Oldest Plant-Eating Dinosaur Has Been Found in India". New York Times. 19 August 2023. Retrieved 23 August 2023.
  3. 1 2 Rauhut, Oliver W. M.; Remes, Kristian; Fechner, Regina; Cladera, Gerardo; Puerta, Pablo (2005-06-02). "Discovery of a short-necked sauropod dinosaur from the Late Jurassic period of Patagonia". Nature. 435 (7042): 670–672. Bibcode:2005Natur.435..670R. doi:10.1038/nature03623. ISSN   1476-4687. PMID   15931221. S2CID   4385136.
  4. Carabajal, Ariana Paulina; Carballido, José L.; Currie, Philip J. (2014-06-07). "Braincase, neuroanatomy, and neck posture of Amargasaurus cazaui (Sauropoda, Dicraeosauridae) and its implications for understanding head posture in sauropods". Journal of Vertebrate Paleontology. 34 (4): 870–882. doi:10.1080/02724634.2014.838174. hdl: 11336/19365 . ISSN   0272-4634. S2CID   85748606.
  5. Xing Xu; Paul Upchurch; Philip D. Mannion; Paul M. Barrett; Omar R. Regalado-Fernandez; Jinyou Mo; Jinfu Ma; Hongan Liu (2018). "A new Middle Jurassic diplodocoid suggests an earlier dispersal and diversification of sauropod dinosaurs". Nature Communications. 9 (1): Article number 2700. Bibcode:2018NatCo...9.2700X. doi:10.1038/s41467-018-05128-1. PMC   6057878 . PMID   30042444.
  6. 1 2 3 4 5 6 7 8 9 10 11 Whitlock, John A. (2011-04-01). "A phylogenetic analysis of Diplodocoidea (Saurischia: Sauropoda)". Zoological Journal of the Linnean Society. 161 (4): 872–915. doi: 10.1111/j.1096-3642.2010.00665.x . ISSN   1096-3642.
  7. Weishampel, DB; Dodson, P; Osmolska, H (2007). The Dinosauria. University of California Press. ISBN   978-0520254084.
  8. 1 2 3 Woodruff, D. Cary; Fowler, Denver W. (2012-07-01). "Ontogenetic influence on neural spine bifurcation in Diplodocoidea (Dinosauria: Sauropoda): a critical phylogenetic character". Journal of Morphology. 273 (7): 754–764. doi:10.1002/jmor.20021. ISSN   1097-4687. PMID   22460982. S2CID   206091560.
  9. 1 2 Harris, Jerald D. (2006-01-01). "The significance of Suuwassea emilieae (Dinosauria: Sauropoda) for flagellicaudatan intrarelationships and evolution". Journal of Systematic Palaeontology. 4 (2): 185–198. doi:10.1017/S1477201906001805. ISSN   1477-2019. S2CID   9646734.
  10. 1 2 3 Tschopp, Emanuel; Mateus, Octávio; Benson, Roger B.J. (2015-04-07). "A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda)". PeerJ. 3: e857. doi: 10.7717/peerj.857 . ISSN   2167-8359. PMC   4393826 . PMID   25870766.
  11. Gallina, Pablo Ariel (2016-09-01). "Reappraisal of the Early Cretaceous sauropod dinosaur Amargatitanis macni (Apesteguía, 2007), from northwestern Patagonia, Argentina". Cretaceous Research. 64: 79–87. doi:10.1016/j.cretres.2016.04.002. hdl: 11336/43971 .
  12. Coria, Rodolfo A; Windholtz, Guillermo J; Ortega, Francisco; Currie, Philip J (2018). "A new dicraeosaurid sauropod from the Lower Cretaceous (Mulichinco Formation, Valanginian, Neuquén Basin) of Argentina". Cretaceous Research. 93: 33–48. doi:10.1016/j.cretres.2018.08.019.
  13. 1 2 3 Sereno, Paul C.; Wilson, Jeffrey A.; Witmer, Lawrence M.; Whitlock, John A.; Maga, Abdoulaye; Ide, Oumarou; Rowe, Timothy A. (2007-11-21). "Structural Extremes in a Cretaceous Dinosaur". PLOS ONE. 2 (11): e1230. Bibcode:2007PLoSO...2.1230S. doi: 10.1371/journal.pone.0001230 . ISSN   1932-6203. PMC   2077925 . PMID   18030355.
  14. Sander, P. Martin; Christian, Andreas; Clauss, Marcus; Fechner, Regina; Gee, Carole T.; Griebeler, Eva-Maria; Gunga, Hanns-Christian; Hummel, Jürgen; Mallison, Heinrich (2011-02-01). "Biology of the sauropod dinosaurs: the evolution of gigantism". Biological Reviews of the Cambridge Philosophical Society. 86 (1): 117–155. doi:10.1111/j.1469-185X.2010.00137.x. ISSN   1469-185X. PMC   3045712 . PMID   21251189.
  15. Salgado, Leonardo; Carvalho, Ismar de Souza; Garrido, Alberto C. (2006). "Zapalasaurus bonapartei, un nuevo dinosaurio saurópodo de La Formación La Amarga (Cretácico Inferior), noroeste de Patagonia, Provincia de Neuquén, Argentina". Geobios. 39 (5): 695–707. doi:10.1016/j.geobios.2005.06.001.
  16. 1 2 Schwarz, Daniela; Kosch, Jens C. D.; Fritsch, Guido; Hildebrandt, Thomas (2015-11-02). "Dentition and tooth replacement of Dicraeosaurus hansemanni (Dinosauria, Sauropoda, Diplodocoidea) from the Tendaguru Formation of Tanzania". Journal of Vertebrate Paleontology. 35 (6): e1008134. doi:10.1080/02724634.2015.1008134. ISSN   0272-4634. S2CID   85579166.
  17. 1 2 Daniela Schwarz-Wings, 10th Annual Meeting of the European Association of Vertebrate Paleontologists. Royo-Torres, R, Gascó, F, and Alcalá, L., coord. ¡Fundamental! 20: 1-290. 2012.

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