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Description
230 million years ago during the Late Triassic period in what is now the Luning Formation of Nevada, USA, some small hydrozoans called Plectodiscus berlinensis float on the surface of the sea while a huge congregation of much bigger animals occurs beneath them. Having swam for days on end from far away, a shoal of Shonisaurus popularis, each one measuring 11 to 16 meters long, have finally reached these waters in massive numbers. While there are few other large animals in these waters for these apex predators to prey on, the ichthyosaurs are not here to eat. Instead, the absence of other such creatures makes this the perfect place for them to give birth, with no predators around to threaten their newborns. Many of the Shonisaurus here are pregnant females, and some have already started going into labour.

Drawing made for Day 9 of the Maysozoic art prompt list, with this day's prompt being Shonisaurus. The ichthyosaurs are an extinct group of reptiles that became adapted for a fully-marine life since the early Triassic, and died out by the middle Cretaceous. As part of adapting to spending all their lives at sea, they developed very shark or dolphin-like bodies and even gave live birth so they wouldn't have to come ashore to lay eggs. The largest ichthyosaurs lived during the Triassic period, early on in the group's evolution, and while not the largest one, Shonisaurus was most certainly huge, reaching possibly up to 16 meters in length. While formerly suggested to take small prey by suction or filter feeding, fossils preserving robust teeth prove that Shonisaurus was macroraptorial, hunting prey like large fish and other marine reptiles.

While known from several locations across North America, fossils of Shonisaurus are most common in the Luning Formation of Nevada, with around 40 individuals represented there, and the area has even been designated as a state park called Berlin-Ichthyosaur State Park because of this (there is a ghost town called Berlin nearby). Curiously, almost no fossil vertebrates other than these ichthyosaurs have been found here, and what little has been found are fragmentary scraps of small fishes, but many invertebrate fossils are known from here. Because both massive ichthyosaurs and tiny invertebrates are found in abundance, it would appear the absence of other large vertebrates is not due to preservation bias and that they actually were mostly absent from the Luning ecosystem, which raises the question of why so many Shonisaurus were gathered in a place where there was basically nothing for them to eat. This question would be answered in a 2022 study which noted that the Shonisaurus fossils at Luning were all either grown adults or newborn/fetal infants, with none of the intermediate juvenile stages represented. This suggests that Luning was a birthing site for the ichthyosaurs, and the absence of large vertebrates meant the area had no predators which would threaten a newborn Shonisaurus, thus these ocean giants would migrate far and wide from their feeding grounds to give birth here in huge congregations. Similar behavior can be seen in various extant oceanic animals like whales, sharks, sea lions and penguins, which will leave their normal feeding grounds and cross oceans to reach their breeding sites.

Among the many invertebrates found in the Luning Formation, one of them is Plectodiscus berlinensis, a cnidarian belonging to the hydrozoan group, and its closest living relatives is believed to be the by-the-wind-sailor (yes that is a real animal, Google it). The one known specimen of this species was actually found attached to the vertebra of a Shonisaurus, and is a circular fossil measuring just over 2 centimeters in diameter. Other Plectodiscus species and modern by-the-wind-sailors have a sail-like structure that catches the wind so they can raft across the ocean surface, and while this has not been found in P. berlinensis, its absence is likely a taphonomic artefact.

Description
230 million years ago during the Late Triassic period in what is now the Luning Formation of Nevada, USA, some small hydrozoans called Plectodiscus berlinensis float on the surface of the sea while a huge congregation of much bigger animals occurs beneath them. Having swam for days on end from far away, a shoal of Shonisaurus popularis, each one measuring 11 to 16 meters long, have finally reached these waters in massive numbers. While there are few other large animals in these waters for these apex predators to prey on, the ichthyosaurs are not here to eat. Instead, the absence of other such creatures makes this the perfect place for them to give birth, with no predators around to threaten their newborns. Many of the Shonisaurus here are pregnant females, and some have already started going into labour.

Drawing made for Day 9 of the Maysozoic art prompt list, with this day's prompt being Shonisaurus. The ichthyosaurs are an extinct group of reptiles that became adapted for a fully-marine life since the early Triassic, and died out by the middle Cretaceous. As part of adapting to spending all their lives at sea, they developed very shark or dolphin-like bodies and even gave live birth so they wouldn't have to come ashore to lay eggs. The largest ichthyosaurs lived during the Triassic period, early on in the group's evolution, and while not the largest one, Shonisaurus was most certainly huge, reaching possibly up to 16 meters in length. While formerly suggested to take small prey by suction or filter feeding, fossils preserving robust teeth prove that Shonisaurus was macroraptorial, hunting prey like large fish and other marine reptiles.

While known from several locations across North America, fossils of Shonisaurus are most common in the Luning Formation of Nevada, with around 40 individuals represented there, and the area has even been designated as a state park called Berlin-Ichthyosaur State Park because of this (there is a ghost town called Berlin nearby). Curiously, almost no fossil vertebrates other than these ichthyosaurs have been found here, and what little has been found are fragmentary scraps of small fishes, but many invertebrate fossils are known from here. Because both massive ichthyosaurs and tiny invertebrates are found in abundance, it would appear the absence of other large vertebrates is not due to preservation bias and that they actually were mostly absent from the Luning ecosystem, which raises the question of why so many Shonisaurus were gathered in a place where there was basically nothing for them to eat. This question would be answered in a 2022 study which noted that the Shonisaurus fossils at Luning were all either grown adults or newborn/fetal infants, with none of the intermediate juvenile stages represented. This suggests that Luning was a birthing site for the ichthyosaurs, and the absence of large vertebrates meant the area had no predators which would threaten a newborn Shonisaurus, thus these ocean giants would migrate far and wide from their feeding grounds to give birth here in huge congregations. Similar behavior can be seen in various extant oceanic animals like whales, sharks, sea lions and penguins, which will leave their normal feeding grounds and cross oceans to reach their breeding sites.

Among the many invertebrates found in the Luning Formation, one of them is Plectodiscus berlinensis, a cnidarian belonging to the hydrozoan group, and its closest living relatives is believed to be the by-the-wind-sailor (yes that is a real animal, Google it). The one known specimen of this species was actually found attached to the vertebra of a Shonisaurus, and is a circular fossil measuring just over 2 centimeters in diameter. Other Plectodiscus species and modern by-the-wind-sailors have a sail-like structure that catches the wind so they can raft across the ocean surface, and while this has not been found in P. berlinensis, its absence is likely a taphonomic artefact.