Crocodiles are great

[Anomotodon]

Crocodylians are some of the most under-appreciated parts of Mesozoic and Cenozoic faunas. While it's a common to assume that they are "living fossils" and barely changed since the Triassic, this is actually false - crocodylians were, and still are, extremely diverse. Systematics of these organisms can be confusing, so in this thread when I say "crocodiles" I mean Crocodylomorphs - a larger clade that includes extant crocodiles and their extinct relatives starting in Triassic.

 

Let's start, of course, with Upper Cretaceous Kem Kem beds in Morocco. Those deposits were home to famous dinosaurs, such as Spinosaurus and Carcharodontosaurus, that ofen overshadow the incredible diversity of local crocodylomorphs.

 

Clade: Crocodylomorpha

Clade: Crocodyliformes

Clade: Metasuchia

Clade: Neosuchia

Family: Pholidosauridae

Species: Elosuchus cherifiensis

Elosuchus was the largest and one of the most common Kem Kem crocodylians.  Its taxonomy is debated, but it was most likely a Pholidosaurid, a member of the family of large, aquatic crocodylomorphs that were close to the base of crocodylomorph phylogeny. Another famous member of this family is Nigerien Sarcosuchus imperator, one of the largest crocodylomorphs.

Unfortunately I don't have any pictures of its teeth at hand, so feel free to add any of your own! I do have this partial premaxilla. Premaxillae of many pholidosaurids can be easily identified because of their bulbous shape. Elosuchus teeth were large and robust, sometimes with enamel ridges.

 

 

Family: Stomatosuchidae

Species: Laganosuchus maghrebiensis

 

In my experience looking at various commercially available Kem Kem fossils, this species is one of the rarest. Laganosuchus was a stomatosuchid - a family of crocodylomorphs with strongly compressed skulls, earning them the name of "pancake" crocodiles. I have a small dentary section, close to the symphysis - connection between left and right halves. I believe it is a stomatosuchid because of how compressed this section is, considerable distance between tooth sockets (alveoli) and short symphysis, as seen in Elosuchus and many other crocodiles.

 

 

Here is a similar L. maghrebiensis dentary fragment with a tooth; and a L. thaumastos tooth (Sereno & Larsson, 2009).

 

 

Here is a lower jaw of L. thaumastos from Niger that displays the "pancake" shape (also Sereno & Larsson, 2009).

 

 

Clade: Metasuchia

Clade: Notosuchia

 

Notosuchians were primarily terrestrial crocodylomorphs, known since the Jurassic but reaching their peak diversity in the Cretaceous. There are a few species known from Kem Kem beds: Hamadasuchus rebouli, Antaeusuchus taouzensis, Araripesuchus rattoides and Lavocatchampsa sigogneaurusselae (unfortunately don't have any specimens from this one). A unique trait of notosuchians is strong heterodonty - differentiation of teeth. Many species had well-defined incisiform, caniniform or molariform teeth, functionally equivalent to incisors, canines and molars in mammals.

 

Family: Peirosauridae

Species: Hamadasuchus reboulli

 

Hamadasuchus was one of the two peirosaurids in Kem Kem, the other one being Antaeusuchus. Antaeusuchus was larger than Hamadasuchus, had less ornamented dentary surface and significantly more robust teeth. Here is a dentary from Hamadasuchus, displaying the diagnostic triangular and labio-lingually compressed posterior tooth. You can read more about the differences between these two taxa in Nicholl et al., 2021.

 

 

Here are a few Hamadasuchus teeth from various tooth positions. Many of these have fine serrations, another characteristic trait of notosuchian teeth. All scalebars are 1 cm.

 

 

 

Family: Uruguaysuchidae

Species: Araripesuchus rattoides

 

Araripesuchus was a small terrestrial notosuchian with gracile anatomy. It also had clear heterodonty but its teeth were considerably smaller than those of Hamadasuchus. Additionally, the dentary was less apico-basally expanded. I have a dentary and a partial maxilla from different individuals. You can clearly see how heterodont this species was from the size of the alveoli.

 

 

Teeth of A. wegeneri from Niger:

 

 

Notosuchia indet.?

 

This is a dentary section that I've been struggling to identify. Its extremely elongated, but certainly not Laganosuchus because it looks like left and right halves were fused along the entire length. Also, alveoli are not spaced enough for Laganosuchus or Elosuchus. The one preserved tooth is strongly compressed and has visible denticles, which points to a notosuchian. However, it could also be Aegisuchus - an aegyptosuchid crocodylomorph, jaws of which are unknown.

 

 

Edited July 21 by Anomotodon

[Mikrogeophagus]

Great post about an underrated group of animals. Loved the pictures and all the serrated teeth! I had a similar post idea for my texas crocs. Might have to make that some time soon. So many neat paths on the family tree

[Anomotodon]

22 minutes ago, Mikrogeophagus said:

Great post about an underrated group of animals. Loved the pictures and all the serrated teeth! I had a similar post idea for my texas crocs. Might have to make that some time soon. So many neat paths on the family tree

Thanks, more coming soon! Would love to see your specimens too - feel free to post them here if you want.

[Anomotodon]

Moving on to other locations.

 

Clade: Notosuchia

Species: Razanandrongobe sakalavae

 

Razanandrongobe is the oldest known notosuchian from the Middle Jurassic Sakaraha (Isalo IIIB) formation of Madagascar. It was a large terrestrial crocodile with robust, coarsely serrated teeth. Not a whole lot is known from it - mostly just parts of the skull. Here is a partial left premaxilla from a juvenile that matches the holotype (see a detailed description of known elements at Dal Sasso et al., 2017). There are three oval-shaped alveoli preserved, and I believe two more are missing. Border of the nostril - external naris, can be seen is the upper third of the anterior end of the bone.

 

 

Notosuchia indet. ?

 

In the Cretaceous, notosuchian diversity reached its peak. While more species are known from Gondwana, some lived further north as well. Here are a few tiny teeth (scale bar 1 mm on all) from some indeterminate notosuchians from the mid-Cretaceous (Cenomanian) Woodbine formation, Texas. No notosuchians were described from this formation, however, morphology of these teeth is similar to small notosuchians such as Araripesuchus. They are labio-lingually compressed and show prominent carinae (it is hard to tell if there are any denticles preserved). May also be atoposaurid (non-notosuchian terrestrial crodylomorphs).

 

 

Family: Mahajangasuchidae

Species: Mahajangasuchus insignis

 

Mahajangasuchus was a large terrestrial crocodyliform from the Late Cretaceous (Maastrichtian) Maevarano formation of Madagascar. Its teeth were ziphodont - meaning they were labio-lingually compressed and some had serrations. Here is tooth from one, scale bar is 1 cm.

 

 

Clade: Sebecosuchia

Family: Iberosuchidae

Species: Iberosuchus macrodon

 

Notosuchians somehow managed to survive the end-Cretaceous mass extinction, and were around in South America until the Miocene. In the Eocene, however, there were still notosuchians in Europe and North America - bergisuchids, sebecids, iberosuchids. Here is a tooth of Iberosuchus macrodon from the Eocene (Bartonian) of Robiac, France. Iberosuchus had large (scale bar 1 cm) and strongly compressed serrated teeth with smooth enamel, much like theropod dinosaurs and unlike many Cretaceous notosuchians.

 

 

Clade: Neosuchia

Clade: Eusuchia

Family: Planocraniidae indet. ?

 

Planocraniids were a group of Cenozoic terrestrial crocodiles that were not notosuchians, but were much more closely related to extant crocodiles in the clade Neosuchia. In the Eocene of Europe and North America they may have shared their environment with contemporary sebecosuchians, such as Iberosuchus. They also possessed a ziphodont dentition that evolved convergently to notosuchians. Here is a possible planocraniid tooth from the Paleocene Aquia formation of Virginia (scale 1 cm).

 

 

Edited July 21 by Anomotodon

[JoshIrving]

On 7/21/2024 at 4:59 AM, Anomotodon said:

Crocodylians are some of the most under-appreciated parts of Mesozoic and Cenozoic faunas. While it's a common to assume that they are "living fossils" and barely changed since the Triassic, this is actually false - crocodylians were, and still are, extremely diverse. Systematics of these organisms can be confusing, so in this thread when I say "crocodiles" I mean Crocodylomorphs - a larger clade that includes extant crocodiles and their extinct relatives starting in Triassic.

 

Let's start, of course, with Upper Cretaceous Kem Kem beds in Morocco. Those deposits were home to famous dinosaurs, such as Spinosaurus and Carcharodontosaurus, that ofen overshadow the incredible diversity of local crocodylomorphs.

 

Clade: Crocodylomorpha

Clade: Crocodyliformes

Clade: Metasuchia

Clade: Neosuchia

Family: Pholidosauridae

Species: Elosuchus cherifiensis

Elosuchus was the largest and one of the most common Kem Kem crocodylians.  Its taxonomy is debated, but it was most likely a Pholidosaurid, a member of the family of large, aquatic crocodylomorphs that were close to the base of crocodylomorph phylogeny. Another famous member of this family is Nigerien Sarcosuchus imperator, one of the largest crocodylomorphs.

Unfortunately I don't have any pictures of its teeth at hand, so feel free to add any of your own! I do have this partial premaxilla. Premaxillae of many pholidosaurids can be easily identified because of their bulbous shape. Elosuchus teeth were large and robust, sometimes with enamel ridges.

 

 

Family: Stomatosuchidae

Species: Laganosuchus maghrebiensis

 

In my experience looking at various commercially available Kem Kem fossils, this species is one of the rarest. Laganosuchus was a stomatosuchid - a family of crocodylomorphs with strongly compressed skulls, earning them the name of "pancake" crocodiles. I have a small dentary section, close to the symphysis - connection between left and right halves. I believe it is a stomatosuchid because of how compressed this section is, considerable distance between tooth sockets (alveoli) and short symphysis, as seen in Elosuchus and many other crocodiles.

 

 

Here is a similar L. maghrebiensis dentary fragment with a tooth; and a L. thaumastos tooth (Sereno & Larsson, 2009).

 

 

Here is a lower jaw of L. thaumastos from Niger that displays the "pancake" shape (also Sereno & Larsson, 2009).

 

 

Clade: Metasuchia

Clade: Notosuchia

 

Notosuchians were primarily terrestrial crocodylomorphs, known since the Jurassic but reaching their peak diversity in the Cretaceous. There are a few species known from Kem Kem beds: Hamadasuchus rebouli, Antaeusuchus taouzensis, Araripesuchus rattoides and Lavocatchampsa sigogneaurusselae (unfortunately don't have any specimens from this one). A unique trait of notosuchians is strong heterodonty - differentiation of teeth. Many species had well-defined incisiform, caniniform or molariform teeth, functionally equivalent to incisors, canines and molars in mammals.

 

Family: Peirosauridae

Species: Hamadasuchus reboulli

 

Hamadasuchus was one of the two peirosaurids in Kem Kem, the other one being Antaeusuchus. Antaeusuchus was larger than Hamadasuchus, had less ornamented dentary surface and significantly more robust teeth. Here is a dentary from Hamadasuchus, displaying the diagnostic triangular and labio-lingually compressed posterior tooth. You can read more about the differences between these two taxa in Nicholl et al., 2021.

 

 

Here are a few Hamadasuchus teeth from various tooth positions. Many of these have fine serrations, another characteristic trait of notosuchian teeth. All scalebars are 1 cm.

 

 

 

Family: Uruguaysuchidae

Species: Araripesuchus rattoides

 

Araripesuchus was a small terrestrial notosuchian with gracile anatomy. It also had clear heterodonty but its teeth were considerably smaller than those of Hamadasuchus. Additionally, the dentary was less apico-basally expanded. I have a dentary and a partial maxilla from different individuals. You can clearly see how heterodont this species was from the size of the alveoli.

 

 

Teeth of A. wegeneri from Niger:

 

 

Notosuchia indet.?

 

This is a dentary section that I've been struggling to identify. Its extremely elongated, but certainly not Laganosuchus because it looks like left and right halves were fused along the entire length. Also, alveoli are not spaced enough for Laganosuchus or Elosuchus. The one preserved tooth is strongly compressed and has visible denticles, which points to a notosuchian. However, it could also be Aegisuchus - an aegyptosuchid crocodylomorph, jaws of which are unknown.

 

 

 

Great post.

 

Here are three teeth from the KemKem group which I believe to be Croc teeth. From the information in your post, I believe they are from either Notosuchia indet. or Hamadasuchus sp.

 

Would love to know your opinion on these.

 

[Anomotodon]

16 hours ago, JoshIrving said:

 

Great post.

 

Here are three teeth from the KemKem group which I believe to be Croc teeth. From the information in your post, I believe they are from either Notosuchia indet. or Hamadasuchus sp.

 

Would love to know your opinion on these.

 

 

Thanks, great teeth! I agree, these seem to be Hamadasuchus reboulli based on how compressed they are.

[Notidanodon]

What an informative post!

[PaleoNoel]

I concur, crocodiles are indeed great.