Tom Beevor
@thomasbeevor.bsky.social
British
Science Technician
Palaeontology Graduate
Science Technician
Palaeontology Graduate
Clidastes is believed to have been replaced by its much larger (15m long) relative Mosasaurus during the wave of mosasaur diversification that took place during the later Campanian stage of the Late Cretaceous.
April 4, 2025 at 11:17 PM
Clidastes is believed to have been replaced by its much larger (15m long) relative Mosasaurus during the wave of mosasaur diversification that took place during the later Campanian stage of the Late Cretaceous.
Clidastes is believed to have been a shallow diver that preyed on smaller fish and marine reptiles with its slender conical teeth. Its proportionally long torso indicates that it was not an especially fast swimmer compared with contemporary mosasaurs Tylosaurus and Platecarpus.
April 4, 2025 at 11:16 PM
Clidastes is believed to have been a shallow diver that preyed on smaller fish and marine reptiles with its slender conical teeth. Its proportionally long torso indicates that it was not an especially fast swimmer compared with contemporary mosasaurs Tylosaurus and Platecarpus.
Clidastes was a relatively small mosasaur (4-5m long) known from the North America and Europe, with the North American population dwelling in the Western Interior Seaway, a shallow inland sea that covered much of the continental Interior during the Late Cretaceous.
April 4, 2025 at 11:15 PM
Clidastes was a relatively small mosasaur (4-5m long) known from the North America and Europe, with the North American population dwelling in the Western Interior Seaway, a shallow inland sea that covered much of the continental Interior during the Late Cretaceous.
Mosasaurids were a family of marine squamate reptiles exclusively found in Late Cretaceous deposits. They were closely related to both snakes and lizards, although the extent of their relationship with either of these groups remains controversial.
April 4, 2025 at 11:13 PM
Mosasaurids were a family of marine squamate reptiles exclusively found in Late Cretaceous deposits. They were closely related to both snakes and lizards, although the extent of their relationship with either of these groups remains controversial.
Late Cretaceous (80 mya), Gober Chalk Formation, Austin Group, Gober, Fannin County, Texas, USA.
April 4, 2025 at 11:11 PM
Late Cretaceous (80 mya), Gober Chalk Formation, Austin Group, Gober, Fannin County, Texas, USA.
For #fossilfriday a caudal (neck) vertebra from the mosasaurine mosasaurid Clidastes (meaning "One who locks up" referencing the bony processes on the vertebra that interlock to stiffen the back of the animal to increase swimming efficiency).
April 4, 2025 at 11:10 PM
For #fossilfriday a caudal (neck) vertebra from the mosasaurine mosasaurid Clidastes (meaning "One who locks up" referencing the bony processes on the vertebra that interlock to stiffen the back of the animal to increase swimming efficiency).
Eurypterus was unable to spread across open ocean, but was able to spread from Baltica (Western Eurasia) to Laurentia (North America) during the Silurian as both continents were joined to form the large supercontinent known as Laurussia.
March 22, 2025 at 2:09 AM
Eurypterus was unable to spread across open ocean, but was able to spread from Baltica (Western Eurasia) to Laurentia (North America) during the Silurian as both continents were joined to form the large supercontinent known as Laurussia.
It is believed that like modern horseshoe crabs, Eurypterus would congregate in hypersaline waters to moult and mate, with the high salinity and large numbers helping to deter predators. This is supported by the fact that most fossils are found in hypersaline dolostone.
March 22, 2025 at 2:09 AM
It is believed that like modern horseshoe crabs, Eurypterus would congregate in hypersaline waters to moult and mate, with the high salinity and large numbers helping to deter predators. This is supported by the fact that most fossils are found in hypersaline dolostone.
Despite the overall rarity of the Eurypterida in Paleozoic faunas, Eurypterus is notably widespread, representing more than 95% of all known eurypterid fossils and can be found in vast numbers in certain assemblages, mostly in the form of moulted body casings.
March 22, 2025 at 2:08 AM
Despite the overall rarity of the Eurypterida in Paleozoic faunas, Eurypterus is notably widespread, representing more than 95% of all known eurypterid fossils and can be found in vast numbers in certain assemblages, mostly in the form of moulted body casings.
The lack of large spines and pincers indicate the small and unspecialized Eurypterus was not an active hunter and was likely a generalist predator and scavenger that fed on other invertebrates such as small eurypterids, trilobites, cephalopods and worms.
March 22, 2025 at 2:08 AM
The lack of large spines and pincers indicate the small and unspecialized Eurypterus was not an active hunter and was likely a generalist predator and scavenger that fed on other invertebrates such as small eurypterids, trilobites, cephalopods and worms.
Eurypterids (commonly known as 'sea scorpions') were a group of predatory chelicerate aquatic arthropods, existing from the Ordovician to the Permian. Despite the name, they are more closely related to horseshoe crabs than true scorpions.
March 22, 2025 at 2:07 AM
Eurypterids (commonly known as 'sea scorpions') were a group of predatory chelicerate aquatic arthropods, existing from the Ordovician to the Permian. Despite the name, they are more closely related to horseshoe crabs than true scorpions.
For #fossilfriday two head shields from the Silurian eurypterid (sea scorpion) genus Eurypterus ("Wide Wing/Broad Paddle")
Left: E. tetragonopthalmus from the (423-427myo) Bagovitsa Formation, Ukraine
Right: E. remipes from the (423-419myo) Fiddlers Green Fm, New York State, USA
Left: E. tetragonopthalmus from the (423-427myo) Bagovitsa Formation, Ukraine
Right: E. remipes from the (423-419myo) Fiddlers Green Fm, New York State, USA
March 22, 2025 at 2:06 AM
For #fossilfriday two head shields from the Silurian eurypterid (sea scorpion) genus Eurypterus ("Wide Wing/Broad Paddle")
Left: E. tetragonopthalmus from the (423-427myo) Bagovitsa Formation, Ukraine
Right: E. remipes from the (423-419myo) Fiddlers Green Fm, New York State, USA
Left: E. tetragonopthalmus from the (423-427myo) Bagovitsa Formation, Ukraine
Right: E. remipes from the (423-419myo) Fiddlers Green Fm, New York State, USA
Nothosaurians were one of the first groups of marine reptiles to appear in the Mesozoic, however they had completely disappeared before the end of the Triassic, replaced by the more fully aquatically adapted Plesiosauria (plesiosauroids and pliosauroids).
March 15, 2025 at 12:20 AM
Nothosaurians were one of the first groups of marine reptiles to appear in the Mesozoic, however they had completely disappeared before the end of the Triassic, replaced by the more fully aquatically adapted Plesiosauria (plesiosauroids and pliosauroids).
Close relatives of the Nothosauria include the diminutive Pachypleurosauria and the more aquatically adapted Pistosauria, the latter of which are believed to be the direct ancestors of the Plesiosauria.
March 15, 2025 at 12:18 AM
Close relatives of the Nothosauria include the diminutive Pachypleurosauria and the more aquatically adapted Pistosauria, the latter of which are believed to be the direct ancestors of the Plesiosauria.
In contrast, the much larger (6m long) coexisting Nothosaurus giganteus had a more robust and laterally expanded skull, possibly as an aid for preying upon larger prey such as other marine reptiles.
March 15, 2025 at 12:17 AM
In contrast, the much larger (6m long) coexisting Nothosaurus giganteus had a more robust and laterally expanded skull, possibly as an aid for preying upon larger prey such as other marine reptiles.
The 3m long Nothosaurus mirabilis had a flexible, flattened tail as well as webbed feet and a broad, flat skull lined with interlocking needle-like teeth. This implies it was a semiaquatic pursuit predator of fish, with a similar lifestyle to modern-day seals.
March 15, 2025 at 12:16 AM
The 3m long Nothosaurus mirabilis had a flexible, flattened tail as well as webbed feet and a broad, flat skull lined with interlocking needle-like teeth. This implies it was a semiaquatic pursuit predator of fish, with a similar lifestyle to modern-day seals.
Nothosaurs are a group of Triassic exclusive semi-aquatic sauropterygian reptiles. They were closely related to the plesiosaurs and pliosaurs but their morphology indicates a more semi-aquatic rather than a fully-aquatic lifestyle.
March 15, 2025 at 12:14 AM
Nothosaurs are a group of Triassic exclusive semi-aquatic sauropterygian reptiles. They were closely related to the plesiosaurs and pliosaurs but their morphology indicates a more semi-aquatic rather than a fully-aquatic lifestyle.
Nothosaurus was a widely distributed animal, with 12 species described from Europe, the Middle East, North Africa and China. These follow the western end of the ancient Tethys Sea as it existed during the Middle Triassic.
March 15, 2025 at 12:14 AM
Nothosaurus was a widely distributed animal, with 12 species described from Europe, the Middle East, North Africa and China. These follow the western end of the ancient Tethys Sea as it existed during the Middle Triassic.
For #Fossilfriday, a small but well-preserved tooth from the nothosaur Nothosaurus mirabilis (meaning “False Lizard”).
Middle Triassic (241-237 mya), Germanic Trias Supergroup, Upper Muschelkalk (limestone). Kircheim, Bavaria, Germany.
Middle Triassic (241-237 mya), Germanic Trias Supergroup, Upper Muschelkalk (limestone). Kircheim, Bavaria, Germany.
March 15, 2025 at 12:13 AM
For #Fossilfriday, a small but well-preserved tooth from the nothosaur Nothosaurus mirabilis (meaning “False Lizard”).
Middle Triassic (241-237 mya), Germanic Trias Supergroup, Upper Muschelkalk (limestone). Kircheim, Bavaria, Germany.
Middle Triassic (241-237 mya), Germanic Trias Supergroup, Upper Muschelkalk (limestone). Kircheim, Bavaria, Germany.
Specimens from Denmark and the Netherlands suggest that Baculites vertebralis may represent the last ammonite species surviving the K-Pg extinction before disappearing in the earliest Paleocene. However, like Enchodus this may in fact represent reworked Cretaceous material.
March 8, 2025 at 1:03 AM
Specimens from Denmark and the Netherlands suggest that Baculites vertebralis may represent the last ammonite species surviving the K-Pg extinction before disappearing in the earliest Paleocene. However, like Enchodus this may in fact represent reworked Cretaceous material.
Complete shell length for adult Baculites ranges from 7cm to 2m, although most specimens only consist of fragmentary chamber sections. These individual chambers are traditionally used as hunting charms by Native Americans due to their resemblance to bison.
March 8, 2025 at 1:02 AM
Complete shell length for adult Baculites ranges from 7cm to 2m, although most specimens only consist of fragmentary chamber sections. These individual chambers are traditionally used as hunting charms by Native Americans due to their resemblance to bison.
With their straight shells, Baculites fossils can appear very similar to older orthoconic nautilus from the Paleozoic, however like all true ammonites, they can be distinguished by the presence of complex suture lines which mark the outlines of individual body chambers (septa).
March 8, 2025 at 1:02 AM
With their straight shells, Baculites fossils can appear very similar to older orthoconic nautilus from the Paleozoic, however like all true ammonites, they can be distinguished by the presence of complex suture lines which mark the outlines of individual body chambers (septa).
Baculites fossils are found worldwide and are especially common in the American Mid-West. During the Late Cretaceous this region would have been covered by the vast and shallow Western Interior Seaway, in which large shoals of Baculites lived.
March 8, 2025 at 1:01 AM
Baculites fossils are found worldwide and are especially common in the American Mid-West. During the Late Cretaceous this region would have been covered by the vast and shallow Western Interior Seaway, in which large shoals of Baculites lived.
Baculites is classed as a heteromorph ammonite, due to its straight shell, which differs from the coiled shells of most ammonites.
Much of the original iridescent shell is still present on both specimens, although most of the actual fossil is the infilled inside of the shell.
Much of the original iridescent shell is still present on both specimens, although most of the actual fossil is the infilled inside of the shell.
March 8, 2025 at 1:00 AM
Baculites is classed as a heteromorph ammonite, due to its straight shell, which differs from the coiled shells of most ammonites.
Much of the original iridescent shell is still present on both specimens, although most of the actual fossil is the infilled inside of the shell.
Much of the original iridescent shell is still present on both specimens, although most of the actual fossil is the infilled inside of the shell.
For #fossilfriday, two shell fragments from the straight shelled ammonite genus Baculites ("Walking Stick Rock").
Left: Baculites ellasi from the Late Cretaceous Pierre Shale Fm, South Dakota, USA.
Right: Baculites compressus from the Late Cretaceous Bearpaw Fm, Montana, USA.
Left: Baculites ellasi from the Late Cretaceous Pierre Shale Fm, South Dakota, USA.
Right: Baculites compressus from the Late Cretaceous Bearpaw Fm, Montana, USA.
March 8, 2025 at 12:59 AM
For #fossilfriday, two shell fragments from the straight shelled ammonite genus Baculites ("Walking Stick Rock").
Left: Baculites ellasi from the Late Cretaceous Pierre Shale Fm, South Dakota, USA.
Right: Baculites compressus from the Late Cretaceous Bearpaw Fm, Montana, USA.
Left: Baculites ellasi from the Late Cretaceous Pierre Shale Fm, South Dakota, USA.
Right: Baculites compressus from the Late Cretaceous Bearpaw Fm, Montana, USA.