There are several archosaurians that have evolved an elongate, narrow rostrum. All of the Crocodylomorphs, and Spinosauridae except for possibly the Bajocian spinosaurid and Ostafrikasaurus crassisseratus possessed an elongated rostrum, this was instrumental in Spinosaurid feeding mechanisms.
Feeding Mechanisms[]
Teeth[]
Spinosaurids are unique theropods in that they are mostly piscivorous dinosaurs, although they were not exclusively piscivores, as a Baryonyx walkeri skeleton was found with an Iguanadon bernissartensis juvenile in it’s digestive tract, a sign of opportunism common in predators today. The teeth of spinosaurs that evolved past the Tithonian were conical, and without serrations, these teeth have been documented in piscivorous crocodilians, elasmosaurids, ornithocheirids, and even piscivorous fish. These teeth were more like a nail than a blade, which means they couldn’t slice flesh, but they could puncture an area of skin.
This was instrumental for spinosaurids success as piscivores, as these types of teeth were evolved for killing fish. The way how these needle like teeth work is simple, theropods with teeth meant for crushing or slicing, like tyrannosauridae or carcharodontosauridae, could catch fish, but the fish would squirm, trying to get back into water. The teeth of spinosaurids would hold the fish in place, while the arms would likely help hold the fish, while other theropods would lose grip of the fish. Pound for pound, the arms of spinosaurids are arguably the most robust part of the body, with large claws, these could hold fish, but a problem with this is that no dinosaurs could pronate(except for potentially hadrosaurids, but that is another matter entirely). The spinosaurids may have had less pressure on pronating, but they would have broken their wrists if they attempted.
Sensory Pores[]
Sasso et al.(2009) noted how the rostrum of MSNM V4047( a Spinosaurus/Sigilmassaurusrostrum) had the presence of tiny pores, similar to modern day crocodilians. These pores were organs when the animal was alive, meant to detect pressure and movement in water. This is an amazing way to sense creatures, yet on an extremely simple principal. The ripples a fish creates when it’s tail and body move would be detected by a spinosaurid in close proximity, leading the spinosaurid with the element of surprise, a key element in being a successful predator.
These features would cause a spinosaurid to lie in wait in the water, with the high raised nostrils being above the water, while the organs in the rostrum would sense for ripples, when a fish was swimming close enough, the spinosaurid would attack at a speed before the fish could react. The needle like teeth would puncture the skin over a small area, creating a lot of pressure, holding the fish in place, then the arms would shred the fish, until the fish stops squirming. Spinosaurids from the Early Cretaceous onward were some of the largest theropods in their ecosystem, so they would eat at their own leisure. The high amount of iron in fish eliminated the need for spinosaurids to actively hunt for other creatures, but they would still occasionally hunt live prey.