Noasaurids were a group of theropod dinosaurs from the Cretaceous Period. They appeared during the Jurassic Period during the Oxfordian towards the end of the Maastrichtian (161-69 Ma). In majority Noasaurs were fairly small with the exception of the oldest Cretaceous noasaurid, Deltadromeus.
Description
Noasaurs were typically small dinosaurs that ranged in size of a house cat, they could reach up to 1 meter with some growing up to 2 meters (6.6ft) in length in the exception of Deltadromeus, which is now known to be largest species of this group. Noasaurids are among the few theropods dinosaurs that evolved in a diversity range of species, acting as the equivalence to groups such as the Maniraptora. Noasaurs were typically piscovores, catching fish using their enlarged conical-like teeth as such with the Masiakasaurus to easily catch and hold prey, it is also suggested by paleontologists that from their unusual dentition that Noasaurs like Masiakasaurus had an omnivorous behavior, suited to eating invertebrates, small vertebrates, fruits. However upon the discovery of the Limusaurus and reclassification of Deltadromeus, that some species were herbivorous and carnivorous. Noasaurids are apart of the Ceratosaur family, laying within the Abelisauroid group thus making them one of the few oddities their evolution, defined as theropods closely related to Noasaurus than to Carnotaurus, Noasaurs varied in different forms, some like Elaphrosaurus resembling dinosaurs like Coelophysis and Struthiomimus and others such as Deltadromeus resembling the Allosaurs or Tyrannosaurs.
Classification
Noasauridae is defined as all theropods closer to Noasaurus than to Carnotaurus. Many species have been referred to Noasauridae, though most are known from extremely fragmentary remains, which makes it difficult to assess their relationships.[2] Many of these species (Composuchus, Jubbulpuria, Ornithomimoides, Vitakrisaurus, Coeluroides) are considered nomen dubia. Nevertheless, some traits can be established for the family as a whole as well as clades and subfamilies within it.
Among Abelisauroids, noasaurids can be distinguished by:[1]
- Low and rectangular neural spines of mid caudals.
- A wide space (over half the length of the glenoid) between the glenoid lip and the posteroventral process of the coracoid.
- A coracoid over 1.8 times as wide as it is long.
- A stout humeral head in proximal view.
- A flat anterior side of the distal end of the tibia.
Among Abelisauroids, noasaurids can be distinguished by:[1]
- Low and rectangular neural spines of mid caudals.
- A wide space (over half the length of the glenoid) between the glenoid lip and the posteroventral process of the coracoid.
- A coracoid over 1.8 times as wide as it is long.
- A stout humeral head in proximal view.
- A flat anterior side of the distal end of the tibia.
Phylogeny
Two subfamilies of the noasauridae family exist, drastically inheriting biological traits, Elaphrosaurinae and Noasaurinae, the best known member Elaphrosaurinae is Limusaurus, a toothless, beaked herbivore with short arms hands, but otherwise had gracile proportions. On the other hand most members like the most complete Noasaurine, Masiakasaurus were carnivorous, had very long teeth and a drastically downturned lower jaw, and rather long arms with raptorial-like hands. Earlier members of the Noasaurid family, the still disputed Deltadromeus and the incomplete Laevisuchus were more outside of these two subfamilies, therefore making them both basal members of the group.
However, both of these groups are united by a reduced fourth trochanter of the femur and (particularly in Noasaurinae) a thin metatarsal II.
Elaphrosaurines are also characterized by cervical vertebrae with concave anterior surfaces, cervical ribs fused to the vertebrae, short ilia in comparison to the femurs, and planar contact between the pubis and illium.[1]
The following cladogram is based on the phylogenetic analysis conducted by Rauhut and Carrano in 2016, showing the relationships among the Noasauridae:[1]
| Abelisauroidea |
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Even in recent studies, the composition of noasauridae has been difficult to resolve. An analysis conducted by Tortosa et al. (2013)[4] recovered Dahalokely as a basal noasaurid.[4] However, another analysis later that year found it to be a basal carnotaurine instead.[1] Similarly, the genus Genusaurus has been found to be a noasaurid by some older studies, but in 2013 was classified as an abelisaurid.[1]Deltadromeus is a particularly controversial genus, as it shares many features with noasaurids but is also very similar to Gualicho, which has been classified as a close relative of the enigmatic (but generally considered non-ceratosaurian) megaraptorans.[5] A 2017 study describing ontogenetic changes in Limusaurus and the affect of juvenile taxa on phylogenetic analyses provided various phylogenetic trees which varied based on which Limusaurus specimens were used. The structure of noasauridae changed greatly depending on the age of the Limusaurus specimens, although it should be noted that Genusaurus and Deltadromeus were resolved as noasaurids in each diagnosis.[6]
Paleoecology
As fossil records have shown, Noasaurids settled for wet environmental biomes such as wetlands, bogs, swamps and rivers. The evidence correlates to many members of this group based upon their morphological traits or the fossil locations they were unearthed from, with such an enriched environment most of these theropods were nourished with water and food alike.