Dinosaurs ruled the land during the Mesozoic Era, but crocodiles and their relatives unquestionably ruled the water. Prehistoric crocodiles are usually relegated to the background as supporting actors or extras in our imagined Mesozoic dramas, but the truth is that they were just as integral to the landscape back then as they are now. Some of you may be familiar with the impressive gigantic prehistoric species like Deinosuchus of the southern United States or Sarcosuchus of northern Africa, both of which grew to be 40 feet long and likely ate dinosaurs for breakfast. However, creatures like these generate a lot of sensationalist attention because they are the exception. I mean just look at them – they’re enormous and scary-looking! The truth is that most prehistoric crocodiles would have looked vaguely similar to the ones that are alive today, and this article concerns probably the most “average” Mesozoic croc of them all – Goniopholis, a 12 foot long prehistoric crocodile which lived in Europe (and possibly North America) during the late Jurassic Period and early Cretaceous Period approximately 155-140 million years ago. If you’re a paleo-artist or a museum exhibit designer, and you’re looking for a basic ordinary bog-standard prehistoric crocodile to stick into your prehistoric landscape, then this is your boy.
So let’s learn some more about this fascinating beast.
The fossilized remains of this prehistoric crocodile were first found in Dorset, England within the Purbeck Limestone, which dates to the earliest part of the Cretaceous Period. In 1841, the famous British anatomist and paleontologist Sir Richard Owen officially named it Goniopholis (Owen 1841, page 289; Salisbury and Naish 2011, pages 309-318). The name Goniopholis means “angled scale”, and it was probably in reference to the polygonal osteoderms which covered its underside – more about them later. The holotype specimen is currently housed within the collections of the British Museum of Natural History in London, England (collection ID code: NHM 3798; formerly NHMUK 3798 or BMNH 3798) (Paleofile. “Goniopholis”).
Illustration of the holotype specimen of Goniopholis crassidens. The specimen consists of part of the lower jaw, several teeth, several vertebrae, osteoderms, and parts of the pelvis. (1879). Public domain image, Wikimedia Commons.
Goniopholis and other members of the family Goniopholididae are described as basal members of the crocodylomorph clade Neosuchia, “the new crocodiles”. As you can guess by the name, these are advanced species which are located rather high up on the branches of the crocodilian tree. The Neosuchians include all modern-day crocodilians (members of the group Crocodylia) and their immediate ancestors (the clade Eosuchia, or “the true crocodiles”).
- Crocodylomorpha “crocodile-shaped”
- Crocodyliformes” “crocodile form”
- Mesoeucrocodylia “middle true crocodiles”
- Metasuchia “the transcending crocodiles”
- Neosuchia “new crocodiles” (Goniopholis is a basal member of this group)
- Eosuchia “true crocodiles”
- Crocodylia “crocodilians”
Technically speaking, only members of the clade Crocodylia can be accurately referred to as “crocodilians”. Thus, Goniopholis, while certainly within the crocodile tree, isn’t actually a true crocodilian.
Modern crocodilians have several parallel rows of small circular or oval-shaped keeled osteoderms covering the top of their neck, back, and part of the tail. By contrast, the more primitive goniopholidids only had two rows of rectangular strip-like osteoderms, with a keel-like flange on each scale’s outer side. When viewed from above, it gave it a pair of parallel ridges running down its back, slowly converging into one row on the tail. The two osteoderms in the front slightly overlapped the two osteoderms behind it, sort of resembling overlapping roof shingles. Additionally, the goniopholidids possessed mosaic-like rows of polygonal osteoderms covering the underside of the neck and belly. Modern-day crocodilians don’t have any armor on the underside of their bodies.
Skeleton of Goniopholis or possibly Amphicotylus (species unknown), on display at the Science Museum of Minnesota, demonstrating the shape and position of the rectangular dorsal osteoderms. Photograph by Justin Tweet. Image used with permission.
Another view of the skeleton of Goniopholis (species unknown) on display at the Science Museum of Minnesota, demonstrating the shape and position of the polygonal ventral osteoderms. Photograph by Mark Ryan. Image used with permission.
The genus Goniopholis is currently divided into four species:
- Goniopholis baryglyphaeus (Late Jurassic; Portugal; Schwarz 2002).
- Goniopholis crassidens (type species; Early Cretaceous; England; Owen 1841).
- Goniopholis kiplingi (Early Cretaceous; England; De Andrade et al 2011).
- Goniopholis simus (Early Cretaceous; Germany; Salisbury et al 1999).
Additionally, fossils which have been referred to the genus Goniopholis but not to any particular species have been found in Spain (Ortega et al 1996), France (Allain et al 2021), Belgium (Martin et al 2016), and Denmark (Schwarz-Wings et al 2009).
So far, no complete specimen of any species of Goniopholis has been found, which makes length difficult to ascertain with 100% certainty. Some species were evidently larger than others. For example, the Portuguese species G. baryglyphaeus had a skull measuring 28.1 cm (11 inches) long, although it must be noted that this is a measurement of a “reconstructed” skull and the actual fragmentary specimen was much shorter. Based upon the length of the skull, and using a ratio of skull length to body length of other crocodilians, it was hypothesized that the animal reached a total length of 2.1 meters (6.9 feet) (Schwarz 2002, pages 191, 205). By contrast, the English species G. kiplingi had a skull length of 47.56 cm (18.72 inches), and the animal was estimated to have attained a total length of 3.47 meters (11.38 feet) (De Andrade et al 2011). The German species G. simus was slightly larger, with a skull measuring 48.55 cm (19.1 inches) (Salisbury et al 1999, page 132), and may have grown as large as 3.62 meters (11.8 feet) given the ratios used to construct the total lengths of other species. On the whole, the genus Goniopholis is often stated to have reached 3.65 meters (12 feet) long.
In addition to being found in Europe, fossils which have been ascribed to Goniopholis (at least in the past) have also been found within the United States. In March 1877, the famed American paleontologist Edward D. Cope of the Philadelphia Academy of Sciences received a letter from Mr. Oramel W. Lucas, a schoolteacher in Cañon City, Colorado. Lucas stated that, while returning from a hunting trip, he found some fossils and very carefully excavated and measured them. He contacted a geology professor in his old hometown of Oberlin, Ohio about what he ought to do with them, and was told that he should contact either Othniel Charles Marsh at Yale University or Edward D. Cope at Philadelphia – the two most renowned paleontologists in America during that time. Cope responded first, and he said that he was willing to pay Lucas to dig up the bones on his behalf (Royal Gorge Regional Museum and History Center. “Make No Bones About It”).
Shortly after this correspondence took place, Cope’s principal adversary Othniel Charles Marsh published a paper in September 1877, within which he described a new genus of prehistoric crocodile which had been found near Morrison, Colorado. Marsh named it Diplosaurus felix, meaning “the lucky double lizard” – a rather puzzling name until you take into account the shape of the vertebrae. Marsh stated that the skull measured 275 mm long, and also described the specimen as possessing a concave bowl-like depression on the anterior and posterior sides of the vertebral centra – the anatomical term for this shape is “amphicoelous”. Marsh’s report stated that the bones had been found in rocks dated to the early Cretaceous Period, deposited during the same stage as the Wealden Group of southern England. However, a report written by Charles Mook which was published in 1925 stated that the rocks where the Diplosaurus fossils had been uncovered actually dated to the late Jurassic Period, which would place it within the Morrison Formation (Marsh 1877, page 254; Mook 1925, pages 324-325). This makes perfect sense, given that the fossils were found very close to the Morrison Formation’s type locality.
The fossils which were found by Mr. Oramel Lucas were also found within the Morrison Formation. Most of the bones which had been found belonged to the sauropod dinosaur Camarasaurus, but there were also remains that were identified as belonging to a crocodile. In 1878, Cope officially named it Amphicotylus lucasii. Amphicotylus means “both-sided cup” in ancient Greek, and it was named in reference to the shape of the animal’s vertebrae, which were also amphicoelous just like with Diplosaurus. The species name was in honor of Mr. Oramel W. Lucas who discovered the site (Cope 1878, pages 391-392).
Several species of Amphicotylus have been found within North America, all within rocks dated to the late Jurassic Period approximately 155-145 MYA (Erickson 2016, page 7). These include the following:
- Amphicotylus gilmorei (Wyoming, USA; Holland 1905; possibly synonymous with A. lucasii, according to Allen 2012)
- Amphicotylus lucasii (type species; Colorado, USA; Cope 1878)
- Amphicotylus milesi (Wyoming, USA; Yoshida et al 2021)
- Amphicotylus stovalli (Oklahoma, USA; Mook 1964)
Of these, Amphicotylus milesi was the largest, with a skull length of 43 cm (16.9 inches) (Yoshida et al 2021). Alligator skulls are usually one-seventh the total body length. Using this ratio, Amphicotylus milesi would have measured 3 meters (10 feet) long.
Skull of Amphicotylus stovalli (formerly Goniopholis stovalli) on display in the Sam Noble Museum of Natural History in Norman, Oklahoma (collection ID code: OMNH 2392). Public domain image, Wikimedia Commons.
Outline drawing of the above specimen. Illustration by Jason R. Abdale (circa 2008).
The late 1800s ushered in some rapid taxonomic revisions to North American goniopholidid crocodiles. In 1888, Edward D. Cope stated, upon further comparison with European crocodile remains, that Amphicotylus and Goniopholis were synonymous, and that the name Goniopholis should take precedence since it was named first (Cope 1888, page 1,106). Then in 1890, the German paleontologist Karl Alfred von Zittel stated that Marsh’s Diplosaurus and Cope’s Amphicotylus were both junior synonyms of Goniopholis (Zittel 1890, pages 676-677). This was re-asserted in 1902 by Oliver Hay (Hay 1902, page 516) and again in 1906 to a greater degree by Samuel W. Williston. Williston proposed that Marsh’s Diplosaurus and Cope’s Amphicotylus were likely the same animal since both were found near each other within rocks dating to similar times. Williston noted that Marsh never listed any autopomorphies (unique anatomical features which only one species has) for Diplosaurus. Therefore, since there was no detailed description of the animal, there was no way to positively ascertain its identity and likewise its status as a unique genus, thus rendering the name Diplosaurus as a nomen nudum. Furthermore, Williston examined the specimens with his own eyes, and became certain that Goniopholis, Diplosaurus, and Amphicotylus were all one-and-the-same, just as Zittel had proposed (Williston 1906, pages 7-8).
Zittel’s synonymy stuck around for over a hundred years, with all goniopholidid crocodiles which had been found within the Northern Hemisphere lumped into the genus Goniopholis. At one time, the genus Goniopholis was composed of nineteen different species (Tetrapod Zoology. “In pursuit of Early Cretaceous crocodyliforms in southern England: ode to Goniopholididae”). However, beginning in the 1980s, concerns were raised that this synonymy may be incorrect (Salisbury and Naish 2011, page 310). In 2010, Eric R. Allen argued that Zittel was mistaken, and that the original division between Goniopholis and Amphicotylus which had been made during the 1870s was correct all along. He stated that the North American species had a different structure to the palate of the upper jaw compared to the European species, and therefore they ought to be grouped into two separate genera. However, in terms of their outward physical appearance, both genera would have been very similar to each other (Allen 2010; Allen 2012).
As mentioned before, remains of Amphicotylus have hitherto been found only within rocks dated to the Late Jurassic. However, teeth which have been ascribed to goniopholidid crocodiles have also been found in North America within rocks dating to the early Cretaceous Period. Numerous goniopholidid crocodile teeth have been recovered within the Yellow Cat Member of the Cedar Mountain Formation, which is dated approximately 139-132 MYA (Kirkland et al 1997, page 76; Kirkland et al 1999, page 206; Kirkland et al 2016, pages 126-127, 133, 137). However, crocodilian teeth tend to be more-or-less the same in shape regardless of what species they belong to, so these teeth have not yet been positively identified as belonging to Amphicotylus or to some other genus. Crocodile specimens which have been recovered from Dalton Wells, Utah within rocks of the upper Yellow Cat Member (135-132 MYA) consist of two teeth and three osteoderms (Britt et al 2009, page 5), but again, it’s currently unknown which species they belonged to. They probably belonged to the genus Amphicotylus, but this diagnosis cannot be proven at the moment. A single crocodile tooth was also found within the contemporaneous or near-contemporaneous Lakota Formation of western South Dakota during the 1890s (Darton 1904, page 389). However, like the enigmatic teeth found within the Cedar Mountain Formation, these teeth are non-diagnostic.
Below is an illustration which I made of Goniopholis. The illustration was made with a black ballpoint pen on printer paper. The generalized palaeoniscoid fish which you see swimming alongside it are based upon either Coccolepis or Morrolepis.
Goniopholis. © Jason R. Abdale (March 8, 2023).
If you would like to purchase a print of this artwork, please visit my page at Fine Art America by clicking this link: https://fineartamerica.com/profiles/jason-abdale.
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