Post by Infinity Blade on Jan 24, 2016 9:38:06 GMT 5
Parahupehsuchus longus
Life reconstruction of Parahupehsuchus longus.
Temporal range: Early Triassic (upper Spathian; ~248Ma)
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
Superclass: Tetrapoda
Clade: Reptiliomorpha
Clade: Amniota
Class: Reptilia or Clade: Sauropsida
Clade: Eureptilia
Clade: Romeriida
Clade: Diapsida
Clade: Neodiapsida
Clade: †Ichthyosauromorpha
Order: †Hupehsuchia
Family: †Hupehsuchidae
Genus: †Parahupehsuchus
Species: †P. longus
Parahupehsuchus ("Hubei crocodile") is an extinct genus of marine reptile (a hupehsuchian) that lived in what is now Yuan'an County, Hubei Province, China during the upper Spathian of the early Triassic ~248 million years ago (Jialingjiang Formation). There is only one species in this genus.[1]
Description:
Parahupehsuchus was a member of a group of reptiles called the hupehsuchians, which had an edentulous snout akin to a beak, double layered neural spines, a heavily ossified skeleton, and were polydactyl.[1]
The holotype specimen measured ~73 centimeters in length, with ~50 centimeters of that being the trunk. The body was longer, yet narrower-hence more slender-than that of Hupehsuchus. Its ribcage was ~65 millimeters deep throughout the trunk, giving it a 'parallel-sided' ribcage unlike the swollen ribcage of Hupehsuchus. Also, Parahupehsuchus had 10 more dorsal vertebrae than Hupehsuchus (28 vs. 38).[1]
Its most unusual feature was its so called "body tube", which was made of highly modified ribs and gastralia. These bones expanded to the point where there was no space between them, just like a turtle. Despite Parahupehsuchus' slender appearance, its body tube would have severely limited flexibility. The double rib articulation would have prevented rib movement. Its limbs were proportionately too small to be the main propulsive organs. Instead, it is likely that, like other hupehsuchians (the tail of Parahupehsuchus is unknown), its tail was its primary locomotory apparatus. This would mean that its method of underwater locomotion resembled that of crocodilians, which have a stiff trunk and a long tail for propulsion. The flipper shape indicates that they were used as steering devices.[1]
There were likewise three layers of dermal ossicles on the trunk. They were somewhat triangular and pointed upward. The first and second layers interlocked with each other while the third layer was composed of ossicles that were larger than and sat upon the ones below.[1]
Given how the dorsal rib couldn't rotate or move fore-and-aft and how there were no intercostal muscles that could move the rib (as there was no room for them), the body cavity's volume couldn't be changed to produce pressure differentiation for respiration via rib motion. Gastralia translation was also impossible, given how largely the ribs and gastralia overlapped. The only viable option would diaphragmaticus muscle and visceral movement (hepatic piston); the holotype does not prove or disprove this idea.[1]
The body tube and dermal ossicles likely evolved as an anti-predator defense.[1]
Implications about Triassic recovery:
That hupehsuchians evolved such an anti-predator defense suggests that there ws a large predator living with them. Indeed, from Yuan'an County, the remains of a ~3-4 meter long eosauropterygian (which could bite the trunk of Parahupehsuchus) were found. Chen et al. (2014) also note that "Apart from Parahupehsuchus, three additional species of hupehsuchians, the ichthyopterygian Chaohusaurus, and two pachypleurosaurs Hanosaurus, and Keichousaurus, are known in the Nanzhang-Yuan’an fauna. All of them are about 1 m or less in total length–note that marine reptiles tend to have long tails so the trunk is much shorter and narrower in these reptiles than in the marine mammals of the same total length. Unlike heavy-built hupehsuchians, Chaohusaurus was lightly built and the pachypleurosaurs had moderately heavy skeletons. Then, there were at least seven species of potential prey marine reptiles with various degrees of body protection, together with at least one large predator. Notably, no fish fossil is known in the Nanzhang-Yuan’an fauna despite the abundance of marine reptiles, narrowing the prey choice for the large sauropterygian. Then, it is most likely that there was predation pressure upon these smaller marine reptiles."
This suggests that potential tetrapod prey with a predator suggests that a marine trophic structure like today's was being established in the late Early Triassic, only 4 million years after the devastating Permian-Triassic extinction event. This suggests that the recovery of marine predators from the P-T event was quicker than thought, resulting in a new trophic level that hadn't existed before.[1]
References:
[1] "A Carapace-Like Bony ‘Body Tube’ in an Early Triassic Marine Reptile and the Onset of Marine Tetrapod Predation" (Chen et al., 2014).
Life reconstruction of Parahupehsuchus longus.
Temporal range: Early Triassic (upper Spathian; ~248Ma)
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
Superclass: Tetrapoda
Clade: Reptiliomorpha
Clade: Amniota
Class: Reptilia or Clade: Sauropsida
Clade: Eureptilia
Clade: Romeriida
Clade: Diapsida
Clade: Neodiapsida
Clade: †Ichthyosauromorpha
Order: †Hupehsuchia
Family: †Hupehsuchidae
Genus: †Parahupehsuchus
Species: †P. longus
Parahupehsuchus ("Hubei crocodile") is an extinct genus of marine reptile (a hupehsuchian) that lived in what is now Yuan'an County, Hubei Province, China during the upper Spathian of the early Triassic ~248 million years ago (Jialingjiang Formation). There is only one species in this genus.[1]
Description:
Parahupehsuchus was a member of a group of reptiles called the hupehsuchians, which had an edentulous snout akin to a beak, double layered neural spines, a heavily ossified skeleton, and were polydactyl.[1]
The holotype specimen measured ~73 centimeters in length, with ~50 centimeters of that being the trunk. The body was longer, yet narrower-hence more slender-than that of Hupehsuchus. Its ribcage was ~65 millimeters deep throughout the trunk, giving it a 'parallel-sided' ribcage unlike the swollen ribcage of Hupehsuchus. Also, Parahupehsuchus had 10 more dorsal vertebrae than Hupehsuchus (28 vs. 38).[1]
Its most unusual feature was its so called "body tube", which was made of highly modified ribs and gastralia. These bones expanded to the point where there was no space between them, just like a turtle. Despite Parahupehsuchus' slender appearance, its body tube would have severely limited flexibility. The double rib articulation would have prevented rib movement. Its limbs were proportionately too small to be the main propulsive organs. Instead, it is likely that, like other hupehsuchians (the tail of Parahupehsuchus is unknown), its tail was its primary locomotory apparatus. This would mean that its method of underwater locomotion resembled that of crocodilians, which have a stiff trunk and a long tail for propulsion. The flipper shape indicates that they were used as steering devices.[1]
There were likewise three layers of dermal ossicles on the trunk. They were somewhat triangular and pointed upward. The first and second layers interlocked with each other while the third layer was composed of ossicles that were larger than and sat upon the ones below.[1]
Given how the dorsal rib couldn't rotate or move fore-and-aft and how there were no intercostal muscles that could move the rib (as there was no room for them), the body cavity's volume couldn't be changed to produce pressure differentiation for respiration via rib motion. Gastralia translation was also impossible, given how largely the ribs and gastralia overlapped. The only viable option would diaphragmaticus muscle and visceral movement (hepatic piston); the holotype does not prove or disprove this idea.[1]
The body tube and dermal ossicles likely evolved as an anti-predator defense.[1]
Implications about Triassic recovery:
That hupehsuchians evolved such an anti-predator defense suggests that there ws a large predator living with them. Indeed, from Yuan'an County, the remains of a ~3-4 meter long eosauropterygian (which could bite the trunk of Parahupehsuchus) were found. Chen et al. (2014) also note that "Apart from Parahupehsuchus, three additional species of hupehsuchians, the ichthyopterygian Chaohusaurus, and two pachypleurosaurs Hanosaurus, and Keichousaurus, are known in the Nanzhang-Yuan’an fauna. All of them are about 1 m or less in total length–note that marine reptiles tend to have long tails so the trunk is much shorter and narrower in these reptiles than in the marine mammals of the same total length. Unlike heavy-built hupehsuchians, Chaohusaurus was lightly built and the pachypleurosaurs had moderately heavy skeletons. Then, there were at least seven species of potential prey marine reptiles with various degrees of body protection, together with at least one large predator. Notably, no fish fossil is known in the Nanzhang-Yuan’an fauna despite the abundance of marine reptiles, narrowing the prey choice for the large sauropterygian. Then, it is most likely that there was predation pressure upon these smaller marine reptiles."
This suggests that potential tetrapod prey with a predator suggests that a marine trophic structure like today's was being established in the late Early Triassic, only 4 million years after the devastating Permian-Triassic extinction event. This suggests that the recovery of marine predators from the P-T event was quicker than thought, resulting in a new trophic level that hadn't existed before.[1]
References:
[1] "A Carapace-Like Bony ‘Body Tube’ in an Early Triassic Marine Reptile and the Onset of Marine Tetrapod Predation" (Chen et al., 2014).
