Post by Tyrannotitan1316 on May 26, 2018 0:05:24 GMT
Scientific Classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Family: Abelisauridae
Subfamily: Carnotaurinae
Tribe: Carnotaurini
Genus: †Pycnonemosaurus (Kellner & Campos, 2002)
Species: P. nevesi (Kellner & Campos, 2002)
Distribution: Adamantina Formation, Brazil
Time Period: Maastrichtian Stage of the Upper Cretaceous (~72.1-66 ma.)
Size: ~8.62-9.24 meters (29.3-30.3 feet), ~1.75 tonnes (1.93 tons)
Discovery and Naming:
The holotype, which was formally described by Alexander W. A. Kellner and Diogenes de Almeida Campos in 2002, is based on five incomplete teeth, seven partial vertebrae, a few fragmentary ribs, a right tibia, partial fibula, and several other kinds of bones. The beast was named in honor of Dr. Ideo Batista Neves, who had passed away in 2000 as well The material found appeared to be that well preserved, sadly. It is likely that exposure to the elements had happened before the bones were found.
The Largest Abelisaur?
Determining which member of the Abelisauridae is the largest has been the subject of many debate and change. However, for the moment, it has been decided. Although it has been widely accepted for a long time that Carnotaurus sasteri was the largest, but a paper by Orlando Nelson Grillo and Rafael Delcourt comes to a different conclusion. Their estimates were ordered like this:
Pycnonemosaurus nevesi (8.9±0.3 meters)
Carnotaurus sasteri (7.8±0.3 meters)
Abelisaurus comahuensis (7.4±0.7 meters)
Ekrixinatosaurus novasi (7.4±0.7 meters)
While these are only estimations at the moment, due to there not being much material on Pycnonemosaurus, the evidence is sufficient to conclude it was actually larger than Carnotaurus and by at good meter as well. Since Pyconemosaurus was closely related to Carnotaurus, it is safe to assume it had some sort of bump, spike, or horn(s) on its head. It also would likely have been slightly more heavily built than C. sasteri.
Diet:
There were several species of sauropod that would have fallen victim to P. nevesi. There was the 13 meter long Adamantisaurus mezzalirai and the 7 meter long Gondwanatitan faustoi. There were other sauropods in the Adamantina Formation, but their fossils predated those P. nevesi by several million years. Being an abelisaur whose bite forces were less formidable compared to that of the tyrannosaurs from the north, Pycnonemosaurus would have likely gone for the softer areas of the sauropod such as the flanks or the neck. It would have inflicted slashing bites to try and make the prey weak from blood loss and then finished it off with a bite to the jugular or crushing the sauropod’s fragile skull. While it is likely that they could have worked in pairs or even family groups, where they could attack something the size of A. mezzalirai, it would have been significantly easier and less dangerous to gang up against a G. faustoi since it is around a meter or two shorter in length and probably a half meter or so in height compared to P. nevesi. A single P. nevesi would probably be able to handle a G. faustoi. If it were a pair, taking down a G. faustoi would have been fairly easy for the most part. Other reasons that they would not have attacked a full grown A. mezzalirai is their arms and their skulls. Unlike the carcharodontosaurs which they replaced, abelisaurs did not have arms that could grasp. Their “arms” consisted of essential just wrists with little stubby “fingers.” The carcharodontosaurs would likely have used their claws to help grip the flanks of the sauropod while they leapt onto the sides of the prey. The abelisaurs could not do this very well as their arms were useless and their skulls and teeth were relatively small and less robust compared to other theropods like the tyrannosaurs and carcharodontosaurs. If a full grown A. mezzalirai was sick or wounded, there is a chance that a hoard of P. nevesi might gather around the sauropod to cut it off from the herd and wait for the sauropod to die or collapse from exhaustion. However, it is fairly unlikely that P. nevesi would risk injury or death trying to fight a larger prey and would instead attack a sub-adult A. mezzalirai or a G. faustoi. They would not be above cannibalism as seen in Majungasaurus crenatissimus. However, this likely would not be a regular occurrence as it can be extremely detrimental to a species and especially if the species is not all that common. Like all predators, abelisaurs would be opportunists. If there were to stumble upon a nest of sauropod hatchlings, they would take advantage of that. The same would go if they found a dead or dying individual of their own species. Here is a link to a fight I created between P. nevesi and G. faustoi.
Contemporary Fauna:
Pycnonemosaurus would have been the unchallenged king of its world. However, there were other predators that lived in its shadow. To start, there was the four meter long baurusuchid Stratiosuchus maxhechti. They would have likely have preyed on hatchlings of Pycnonemosaurus as well as those of the sauropods Adamantisaurus and Gondwanatitan. A group of S. maxhechti could also have possibly hunted a lone Gondwanatitan. There was also the meter long notosuchid Mariliasuchus spp. There are two species in the genus known: M. amarali and M. robustus. They might have also preyed on dinosaur eggs or hatchlings, but likely would have fallen prey to Stratiosuchus as well as sub adult Pycnonemosaurus.
Extinction:
The rocks of the Adamantina Formation where P. nevesi has been found is from the Maastrichtian stage of the Upper Cretaceous. This dates to 70 ma. Until more evidence is found of P. nevesi, we cannot be sure if it was replaced by another abelisaur or if it died with the rest of the non-avian dinosaurs at the end of the Cretaceous.
Conclusion:
For the longest time, I had thought that the abelisaurs were a boring, useless, and lowly group of theropods. This is because my favorite branch of theropods was (and still is) the carnosaurs and the abelisaurs replaced them. However, I have developed a huge fascination with these creatures after researching their king: Pycnonemosaurus. I found this beast extremely interesting to research and it really warmed me up to the abelisaurs.
References:
Delcourt, R. (2017). Revised morphology of Pycnonemosaurus nevesi Kellner & Campos, 2002
(Theropoda: Abelisauridae) and its phylogenetic relationships. Zootaxa, 4276(1), 1-45.
Grillo, O.N., & Delcourt, R. (2017). Allometry and body length of abelisauroid theropods:
Pycnonemosaurus nevesi is the new king. Cretaceous Research, 69, 71-89.
Kellner, A.W.A., & Campos, D.A. (2002). On a theropod dinosaur (Abelisauria) from the
continental Cretaceous of Brazil. Arquivos do Museu Nacional, Rio de Janeiro, 60(3),
163-170.
RIFF, D., & KELLNER, A. W. (2012, January 12). Baurusuchid crocodyliforms as theropod
mimics: clues from the skull and appendicular morphology of Stratiotosuchus maxhechti
(Upper Cretaceous of Brazil). Retrieved March 09, 2018, from onlinelibrary.wiley.com/doi/10.1111/j.1096-3642.2011.00713.x/full
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Dinosauria
Order: Saurischia
Suborder: Theropoda
Family: Abelisauridae
Subfamily: Carnotaurinae
Tribe: Carnotaurini
Genus: †Pycnonemosaurus (Kellner & Campos, 2002)
Species: P. nevesi (Kellner & Campos, 2002)
Distribution: Adamantina Formation, Brazil
Time Period: Maastrichtian Stage of the Upper Cretaceous (~72.1-66 ma.)
Size: ~8.62-9.24 meters (29.3-30.3 feet), ~1.75 tonnes (1.93 tons)
Discovery and Naming:
The holotype, which was formally described by Alexander W. A. Kellner and Diogenes de Almeida Campos in 2002, is based on five incomplete teeth, seven partial vertebrae, a few fragmentary ribs, a right tibia, partial fibula, and several other kinds of bones. The beast was named in honor of Dr. Ideo Batista Neves, who had passed away in 2000 as well The material found appeared to be that well preserved, sadly. It is likely that exposure to the elements had happened before the bones were found.
The Largest Abelisaur?
Determining which member of the Abelisauridae is the largest has been the subject of many debate and change. However, for the moment, it has been decided. Although it has been widely accepted for a long time that Carnotaurus sasteri was the largest, but a paper by Orlando Nelson Grillo and Rafael Delcourt comes to a different conclusion. Their estimates were ordered like this:
Pycnonemosaurus nevesi (8.9±0.3 meters)
Carnotaurus sasteri (7.8±0.3 meters)
Abelisaurus comahuensis (7.4±0.7 meters)
Ekrixinatosaurus novasi (7.4±0.7 meters)
While these are only estimations at the moment, due to there not being much material on Pycnonemosaurus, the evidence is sufficient to conclude it was actually larger than Carnotaurus and by at good meter as well. Since Pyconemosaurus was closely related to Carnotaurus, it is safe to assume it had some sort of bump, spike, or horn(s) on its head. It also would likely have been slightly more heavily built than C. sasteri.
Diet:
There were several species of sauropod that would have fallen victim to P. nevesi. There was the 13 meter long Adamantisaurus mezzalirai and the 7 meter long Gondwanatitan faustoi. There were other sauropods in the Adamantina Formation, but their fossils predated those P. nevesi by several million years. Being an abelisaur whose bite forces were less formidable compared to that of the tyrannosaurs from the north, Pycnonemosaurus would have likely gone for the softer areas of the sauropod such as the flanks or the neck. It would have inflicted slashing bites to try and make the prey weak from blood loss and then finished it off with a bite to the jugular or crushing the sauropod’s fragile skull. While it is likely that they could have worked in pairs or even family groups, where they could attack something the size of A. mezzalirai, it would have been significantly easier and less dangerous to gang up against a G. faustoi since it is around a meter or two shorter in length and probably a half meter or so in height compared to P. nevesi. A single P. nevesi would probably be able to handle a G. faustoi. If it were a pair, taking down a G. faustoi would have been fairly easy for the most part. Other reasons that they would not have attacked a full grown A. mezzalirai is their arms and their skulls. Unlike the carcharodontosaurs which they replaced, abelisaurs did not have arms that could grasp. Their “arms” consisted of essential just wrists with little stubby “fingers.” The carcharodontosaurs would likely have used their claws to help grip the flanks of the sauropod while they leapt onto the sides of the prey. The abelisaurs could not do this very well as their arms were useless and their skulls and teeth were relatively small and less robust compared to other theropods like the tyrannosaurs and carcharodontosaurs. If a full grown A. mezzalirai was sick or wounded, there is a chance that a hoard of P. nevesi might gather around the sauropod to cut it off from the herd and wait for the sauropod to die or collapse from exhaustion. However, it is fairly unlikely that P. nevesi would risk injury or death trying to fight a larger prey and would instead attack a sub-adult A. mezzalirai or a G. faustoi. They would not be above cannibalism as seen in Majungasaurus crenatissimus. However, this likely would not be a regular occurrence as it can be extremely detrimental to a species and especially if the species is not all that common. Like all predators, abelisaurs would be opportunists. If there were to stumble upon a nest of sauropod hatchlings, they would take advantage of that. The same would go if they found a dead or dying individual of their own species. Here is a link to a fight I created between P. nevesi and G. faustoi.
Contemporary Fauna:
Pycnonemosaurus would have been the unchallenged king of its world. However, there were other predators that lived in its shadow. To start, there was the four meter long baurusuchid Stratiosuchus maxhechti. They would have likely have preyed on hatchlings of Pycnonemosaurus as well as those of the sauropods Adamantisaurus and Gondwanatitan. A group of S. maxhechti could also have possibly hunted a lone Gondwanatitan. There was also the meter long notosuchid Mariliasuchus spp. There are two species in the genus known: M. amarali and M. robustus. They might have also preyed on dinosaur eggs or hatchlings, but likely would have fallen prey to Stratiosuchus as well as sub adult Pycnonemosaurus.
Extinction:
The rocks of the Adamantina Formation where P. nevesi has been found is from the Maastrichtian stage of the Upper Cretaceous. This dates to 70 ma. Until more evidence is found of P. nevesi, we cannot be sure if it was replaced by another abelisaur or if it died with the rest of the non-avian dinosaurs at the end of the Cretaceous.
Conclusion:
For the longest time, I had thought that the abelisaurs were a boring, useless, and lowly group of theropods. This is because my favorite branch of theropods was (and still is) the carnosaurs and the abelisaurs replaced them. However, I have developed a huge fascination with these creatures after researching their king: Pycnonemosaurus. I found this beast extremely interesting to research and it really warmed me up to the abelisaurs.
References:
Delcourt, R. (2017). Revised morphology of Pycnonemosaurus nevesi Kellner & Campos, 2002
(Theropoda: Abelisauridae) and its phylogenetic relationships. Zootaxa, 4276(1), 1-45.
Grillo, O.N., & Delcourt, R. (2017). Allometry and body length of abelisauroid theropods:
Pycnonemosaurus nevesi is the new king. Cretaceous Research, 69, 71-89.
Kellner, A.W.A., & Campos, D.A. (2002). On a theropod dinosaur (Abelisauria) from the
continental Cretaceous of Brazil. Arquivos do Museu Nacional, Rio de Janeiro, 60(3),
163-170.
RIFF, D., & KELLNER, A. W. (2012, January 12). Baurusuchid crocodyliforms as theropod
mimics: clues from the skull and appendicular morphology of Stratiotosuchus maxhechti
(Upper Cretaceous of Brazil). Retrieved March 09, 2018, from onlinelibrary.wiley.com/doi/10.1111/j.1096-3642.2011.00713.x/full