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Description
112 million years ago during the early Cretaceous period, a large dead pliosaur washes up ashore in what is now the Romualdo Formation of Brazil. The massive carcass attracts a pair of Irritator challengeri, a type of spinosaurid dinosaur that feeds mainly on fish, but won't turn down this easy meal. As they feed, they are joined by a smaller dinosaur, Aratasaurus museunacionali, which also tears out bits of flesh to eat. But this annoys the spinosaurs, and one opens its jaws and roars at the smaller dinosaur. Aside from the sound, the sudden flash of color also startles the Aratasaurus into fleeing for now, but it will almost surely return to eat more later.

Drawing for Day 11 of the Maysozoic art prompt list, with this day's prompt being Irritator. The spinosaurids are an unusual family of dinosaurs, with long slender jaws and enlarged hand claws, believed to be adaptations for eating aquatic prey like fish. Some species also had sail-like structures running down their backs, and Spinosaurus, the namesake of the group, was so specialized that it even had a paddle-like tail and shortened hind limbs. Irritator is a spinosaur from Early Cretaceous Brazil, and while its fossil remains aren't complete enough to confirm, it could have similarly had these adaptations considering it was a very close relative of Spinosaurus (even within the spinosaurid family). Known material of Irritator includes the skull of a subadult, which is one of the most well-preserved spinosaur skulls known, and a study of it published in 2023 (linked here ) found that the animals lower jaw would have widened sideways when its mouth was opened. While this may sound weird, cranial kinesis (the movement of skull bones relative to each other) in the lower jaw is actually quite common among reptiles, including birds, and especially in fish-eating species (see this cormorant for example), allowing the animal to swallow bigger prey whole. While Irritator had sharp teeth and claws that would be able to tear flesh, being able to swallow bigger food items would probably still be beneficial, though birds like cormorants and pelicans do sometimes overestimate themselves and try to swallow things they physically cannot (like the Irritator trying to swallow the pliosaur flipper whole). I decided to depict the inside of the mouth as bright blue like that of a double-crested cormorant, since I imagine the large area could be used in display, and the fact that it wouldn't be visible when the mouth is shut means it wouldn't interfere with the camouflage a predator needs to ambush prey.

Aratasaurus is another dinosaur from the Romualdo Formation, known only from remains of a juvenile that was around 3 meters long when it died, and is placed in the coelurosaur group as a close relative of Zuolong from the Jurassic of China. The known specimen was kept in the National Museum of Brazil which burned down in 2018, leading to the destruction of many items kept within, but the Aratasaurus specimen managed to remain intact, hence the genus was given a name meaning "lizard born from fire" in 2020. Regarding the pliosaur carcass, to my knowledge no pliosaur remains are known from the Romualdo Formation, but this group of marine reptiles was widespread during the early Cretaceous and Romualdo was a coastal area, so I guess it's not unreasonable to think one could have washed up dead here. I originally wanted to use Monquirasaurus boyacensis from the Paja Formation of Colombia since it's at least an Early Cretaceous South American species, but then learned that the youngest Paja deposits are just barely older than Romualdo, so this will have to be a hypothetical relative instead. Also the background pterosaurs are Anhanguera piscator, and yeah I totally plucked them out of my other Irritator illustration because I didn't feel like drawing them from scratch just for a background creature when I already had them lying around.

Description
112 million years ago during the early Cretaceous period, a large dead pliosaur washes up ashore in what is now the Romualdo Formation of Brazil. The massive carcass attracts a pair of Irritator challengeri, a type of spinosaurid dinosaur that feeds mainly on fish, but won't turn down this easy meal. As they feed, they are joined by a smaller dinosaur, Aratasaurus museunacionali, which also tears out bits of flesh to eat. But this annoys the spinosaurs, and one opens its jaws and roars at the smaller dinosaur. Aside from the sound, the sudden flash of color also startles the Aratasaurus into fleeing for now, but it will almost surely return to eat more later.

Drawing for Day 11 of the Maysozoic art prompt list, with this day's prompt being Irritator. The spinosaurids are an unusual family of dinosaurs, with long slender jaws and enlarged hand claws, believed to be adaptations for eating aquatic prey like fish. Some species also had sail-like structures running down their backs, and Spinosaurus, the namesake of the group, was so specialized that it even had a paddle-like tail and shortened hind limbs. Irritator is a spinosaur from Early Cretaceous Brazil, and while its fossil remains aren't complete enough to confirm, it could have similarly had these adaptations considering it was a very close relative of Spinosaurus (even within the spinosaurid family). Known material of Irritator includes the skull of a subadult, which is one of the most well-preserved spinosaur skulls known, and a study of it published in 2023 (linked here ) found that the animals lower jaw would have widened sideways when its mouth was opened. While this may sound weird, cranial kinesis (the movement of skull bones relative to each other) in the lower jaw is actually quite common among reptiles, including birds, and especially in fish-eating species (see this cormorant for example), allowing the animal to swallow bigger prey whole. While Irritator had sharp teeth and claws that would be able to tear flesh, being able to swallow bigger food items would probably still be beneficial, though birds like cormorants and pelicans do sometimes overestimate themselves and try to swallow things they physically cannot (like the Irritator trying to swallow the pliosaur flipper whole). I decided to depict the inside of the mouth as bright blue like that of a double-crested cormorant, since I imagine the large area could be used in display, and the fact that it wouldn't be visible when the mouth is shut means it wouldn't interfere with the camouflage a predator needs to ambush prey.

Aratasaurus is another dinosaur from the Romualdo Formation, known only from remains of a juvenile that was around 3 meters long when it died, and is placed in the coelurosaur group as a close relative of Zuolong from the Jurassic of China. The known specimen was kept in the National Museum of Brazil which burned down in 2018, leading to the destruction of many items kept within, but the Aratasaurus specimen managed to remain intact, hence the genus was given a name meaning "lizard born from fire" in 2020. Regarding the pliosaur carcass, to my knowledge no pliosaur remains are known from the Romualdo Formation, but this group of marine reptiles was widespread during the early Cretaceous and Romualdo was a coastal area, so I guess it's not unreasonable to think one could have washed up dead here. I originally wanted to use Monquirasaurus boyacensis from the Paja Formation of Colombia since it's at least an Early Cretaceous South American species, but then learned that the youngest Paja deposits are just barely older than Romualdo, so this will have to be a hypothetical relative instead. Also the background pterosaurs are Anhanguera piscator, and yeah I totally plucked them out of my other Irritator illustration because I didn't feel like drawing them from scratch just for a background creature when I already had them lying around.