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Matthew's Giant Salamander


Carnoferox

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The Chinese giant salamander, living relative of the extinct Matthew's giant salamander. Image courtesy of the University of California, Berkeley.

Abbreviations: NALMA (North American Land Mammal Age), ICS (International Commission on Stratigraphy), AMNH (American Museum of Natural History), UNSM (University of Nebraska State Museum), UCMP (University of California Museum of Paleontology), KU (University of Kansas), ROM (Royal Ontario Museum)

During the middle Miocene, a monster amphibian lurked in North America's waterways. Matthew's giant salamander, Andrias matthewi, has been estimated to have reached up to 2.3 meters (7.5 feet) in length. An extinct relative of the modern giant salamanders, it was the largest salamander of all time. It was an aquatic predator that would have preyed on fish, turtles, amphibians, and even small mammals. Although an obscure taxon, Matthew's giant salamander is a fascinating creature.

Taxonomy and Classification

Matthew's giant salamander belongs to the genus Andrias, which includes two living species, A. davidianus (Chinese giant salamander) and A. japonicus (Japanese giant salamander). A. matthewi was named for paleontologist William Diller Matthew. Andrias belongs to the clade Cryptobranchidae, which includes one other living species, Cryptobranchus alleganiensis (hellbender). Naylor suggested that Andrias and Cryptobranchus represent one genus, but this has been refuted. Synonyms of Andrias matthewi include Plicagnathus matthewi, Cryptobranchus mccalli, and Cryptobranchus matthewi.

Time Period

A. matthewi existed from the upper Hemingfordian through medial Barstovian stages of NALMA, from approximately 16.4 to 13.6 million years ago. This roughly corresponds to the Langhian stage of the ICS geologic timescale. This was during a period known as the Miocene climatic optimum, when average temperatures were 3-5 degrees Celsius higher due to high atmospheric CO2 levels. This allowed the ectothermic Matthew's giant salamander to live at a higher latitudes.

 

Specimens

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A sketch of AMNH 8303, the holotype of Plicagnathus (=Andrias) matthewi. Image courtesy of Meszoely 1966.

The holotype specimen, a fragment of the left dentary (AMNH 8303), was described from the Hemingfordian Mesoceras Quarry of the Snake Creek Formation of Nebraska. A right dentary (AMNH 8361) is known from an unspecified locality near Agate, Nebraska, likely belonging to the Hemingfordian Upper Marsland/Runningwater Formation. These remains were originally referred to as Plicagnathus matthewi by Cook. The second holotype and paratype, a right maxilla (UNSM 61000) and fragmentary left maxilla (UNSM 61001), were described from the Barstovian Norden Bridge Quarry of the Valentine Formation of Nebraska. These remains were originally referred to as Cryptobranchus mccalli by Tihen and Chantell. A left maxilla (UCMP 37165) and left maxillary fragment (UNSM 61044) are known from the Hemingfordian Havorka Quarry of the Upper Marsland/Runningwater Formation in Nebraska. A left maxilla, five vertebrae, two dentary fragments, and a right exoccipital (KU 12004) are known from the Hemingfordian Quarry A in Colorado, also from the Upper Marsland/Runningwater Formation. Meszoely referred all of these specimens to Andrias matthewi. Additionally, two large vertebra (ROM 12727) from the Barstovian Wood Mountain Formation of Saskatchewan were referred to Cryptobranchus matthewi by Naylor.

Size

A size comparison by me between Andrias matthewi and a human.

Based on the original specimens (AMNH 8303 and 8361), Cook estimated a length of around 1.5 meters (5 feet). Based on additional remains and living relatives, Meszoely estimated 1.8 meters (5.9 feet). Based on the two large vertebrae from Saskatchewan (ROM 12727), Naylor calculated a length of up to 2.3 meters (7.5 feet). 

Environment

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A reconstruction of Andrias matthewi from Fossil Salamanders of North America by J. A. Holman.

According to Estes, Matthew's giant salamander would have inhabited the small ponds and streams that were common in middle Miocene North America. During the Miocene climatic optimum, North America would have been covered in subtropical forests and wetlands, similar to modern-day Florida. The best indicator of the environment of A. matthewi is the Norden Bridge Quarry in Nebraska. Norden Bridge, part of the Barstovian Valentine Formation, is a fluvial deposit comprised of channel sandstone. Among the aquatic fauna preserved are alligators (Alligator sp.), alligator gar (Atractosteus spatula), pike (Esox sp.) and alligator snapping turtles (Macrochelys sp.), all potential competitors of A. matthewi. Potential prey for Matthew's giant salamander would include fish like the bowfin (Amia calva), channel catfish (Ictalurus lambda), and sunfish (Lepomis microlophus), turtles like the painted turtle (Chrysemys sp.) and giant soft-shelled turtle (Axestemys quinni), and amphibians like the leopard frog (Rana pipiens) and spadefoot toad (Spea bombifrons). Among the terrestrial fauna are proboscideans (Gomphotherium osborni, Zygolophodon sp.), horses (Merychippus insignis, Parahippus cognatus), rhinos (Aphelops megalodus, Teleoceras meridianum), camels (Procamelus occidentalis, Aepycamelus robustus), chalicotheres (Chalicotheriidae indet.), tapirs (Tapiridae indet.), pronghorns (Merycodus necatus, Ramoceros osborni) and canids (Leptocyon vafer). As evidenced by fossils found at Norden Bridge, Matthew's giant salamander was part of a very diverse and thriving ecosystem.

Extinction

Following the Miocene climatic optimum (roughly 17-14 million years ago) was an extinction event known as Miocene disruption. Between 14 and 13 million years ago, global temperatures dropped due to a decline in CO2 levels. The forests and wetlands that had spread across North America were replaced by dry grasslands. Many species were affected, with ectotherms like reptiles and amphibians being hit the hardest. One of the casualties of this event was Matthew's giant salamander. Unable to cope with lower temperatures and a changing environment, Andrias matthewi went extinct around 13.6 million years ago.

Sources:

  • Cook, H. J. 1917. First recorded amphibian from the Tertiary of Nebraska. Bulletin of the Geological Society of America, 28: 213.
  • Estes, R. 1981. Handbuch der Paläoherpetologie. Teil 2. Gymnophiona, Caudata (Encyclopedia of Paleoherpetology, Part 2, Gymnophiona, Caudata). Stuttgart: Gustav Fischer Verlag.
  • Holman, J. A. 2006. Fossil Salamanders of North America. Bloomington: Indiana UP.
  • M. R. Voorhies. 1990. Vertebrate paleontology of the proposed Norden Reservoir Area, Brown, Cherry and Keya Paha counties, Nebraska. Technical Report, Division of Archaeological Research, Department of Anthropology, University of Nebraska, 82 (9): 1-138
Edited by Saru
Image removed due to browser crashing issue
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Aw no, it's not ugly. It's kinda cute as far as monster amphibians go. Look at it's little feet!

Thanks for the information, by the way. It was quite interesting.

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42 minutes ago, Carnivorfox said:

Not a fish, but still pretty ugly.

For me... everything slimy is a fish.  I've voted for fish to represent me!

(These pain meds I'm on are making me hallucinate.  You reckon I should stop swallowing them and give them back to the hospital pharmacy?)

Edited by Eldorado
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