What do you call a massive prehistoric reptilian tyrant, with large, powerful jaws and sharp serrated teeth?<\/p>\n
If you said Tyrannosaurus rex, that\u2019s understandable: it\u2019s the most famous dinosaurian predator ever. But this mystery beast swam the ocean depths, where no land-stalking Tyrannosaurus ever dove. What would you call that?<\/p>\n
If you said \u201cT. rex,\u201d you\u2019d be correct!<\/p>\n
Paleontologists have discovered an enormous new species of Tylosaurus, a sea lizard belonging to the mosasaur family. Measuring up to 43 feet long\u2014the size of a humpback whale\u2014this 80-million-year-old apex predator is among the biggest known mosasaurs.<\/p>\n
They named it Tylosaurus rex, or \u201cking of the Tylosaurs,\u201d a name that comes with an iconic abbreviation.<\/p>\n
\u201cIf any animal deserves it, it\u2019s this animal,\u201d says Amelia Zietlow<\/a>, a paleontologist previously at the American Museum of Natural History in New York and now at the History Museum at the Castle<\/a> in Wisconsin. \u201cHalf of its characteristics are around it having a bigger jaw and bite.\u201d<\/p>\n Zietlow and her colleagues announced the new underwater terror Thursday in the journal Bulletin of the American Museum of Natural History<\/a>. The finding helps paleontologists better understand the evolution of these enormous sea lizards, including how and when separate lineages of them achieved success as massive marine monsters.<\/p>\n (The 80-foot-long Ichthyotitan was the killer whale of its time<\/a>)<\/p>\n \u201cTylosaurs are already notorious for being one of the largest-sized mosasaurs that ever lived,\u201d says Tiago Sim\u00f5es<\/a>, an evolutionary biologist at Princeton University. \u201cI think this study further supports that, making them the largest group of mosasaurs that ever lived.\u201d<\/p>\n In addition to describing the new species, Zietlow and her team also assembled a comprehensive dataset on mosasaur anatomy, updating the older, rickety version from scratch with head-to-tail measurements of 300 mosasaur specimens and modern lizards<\/p>\n \u201cI hope people are able to use it and give tylosaurs the attention I don\u2019t think they\u2019ve had,\u201d says Zietlow.<\/p>\n Measuring sea monsters<\/p>\n The first known Tylosaurus species, T. proriger (\u201cprow-bearing knob lizard\u201d), was named 150 years ago for the battering-ram-like tips of its jaws. At around 30 feet long, \u201cit was the largest North American mosasaur known for quite some time,\u201d says Mike Polcyn<\/a>, a vertebrate paleontologist at Southern Methodist University and an author on the study. \u201cBecause the snout was so easily recognizable, people could differentiate it easily from other mosasaurs.\u201d<\/p>\n While paleontologists have described other species of Tylosaurus over the years, most of the specimens found in the 84-million-year-old rocks of Kansas are assigned to T. proriger. By custom, several giant specimens originally found in the 80-million-year-old rocks around Dallas, Texas, including a large one now mounted at the Perot Museum of Nature and Science, were also given this classification.<\/p>\n In the 1960s, a Texas paleontologist named John Thurmond wondered in a personal letter whether the largest T. proriger specimens might be their own species, which he half-jokingly dubbed \u201cTylosaurus thallasotyrannus,\u201d or \u201csea tyrant.\u201d But he never formally published the idea.<\/p>\n (This sea monster sank ships off Constantinople for 50 years\u2014was it an orca?<\/a>)<\/p>\n In 2010, when Polcyn received a donation of an immense Tylosaurus specimen from an amateur fossil hunter who had collected it near the city, something about its features struck him as odd. As a side project, he spent years accumulating additional specimens from fossil hunters and reviewing other Texas collections in Austin and Waco. Increasingly, he noticed repeated anatomical traits \u201cthat were clearly pointing to something that was not T. proriger,\u201d he says.<\/p>\n Zietlow was also studying mosasaurs, first as an undergraduate, then as part of her doctoral research at the AMNH. Looking over the AMNH\u2019s extensive collection of Tylosaurus fossils, a big specimen originally collected from Texas also jumped out at her. When, in 2022, Polcyn came on as an outside advisor for her dissertation, she asked him about it. Polcyn initially played it coy, Zietlow says. Then he told her he had tracked down several such colossal specimens.<\/p>\n Zietlow spent the next few years visiting several institutions in Texas, New York, and Massachusetts to remeasure many of their Tylosaurus fossils. The team found that more than a dozen of the largest Tylosaurus specimens held in various museums\u2014including the 31-foot-long \u201cHeath Mosasaur\u201d at the Perot Museum<\/a>, \u201cSophie\u201d at Yale Peabody Museum<\/a>, and the enormous \u201cBunker Mosasaur<\/a>\u201d at the University of Kansas National History Museum\u2014shared similar unusual features. They all had finely serrated teeth, an unusual trait in mosasaurs. All had adaptations in their skull and neck linked to more powerful jaws.<\/p>\n \u201cIt was pretty clear that this thing was consistently different,\u201d Zietlow says.<\/p>\n To make sure these giants weren\u2019t just adult T. proriger, as she had initially assumed in her undergrad work, Zietlow also measured the skeletons of 130 modern lizard species, examining skull features that change over their lifespans. The anatomical differences seen between T. proriger and the large Tylosaurus were not the same features that changed as lizards grew. That, in addition to the four-million-year time difference they had with T. proriger, suggested that the big Texas Tylosaurus were their own species, Zietlow says.<\/p>\n Naming a new T. rex<\/p>\n While the largest T. proriger specimens max out at about 30 feet long, T. rex specimens all ranged from 25 feet to 43 feet.<\/p>\n It was \u201ca danged big lizard,\u201d says Ron Tykoski, a curator at the Perot Museum and author of the paper. T. rex (the sea lizard) seems to have been a formidable and aggressive animal. One of several specimens held at the Perot Museum in Dallas, nicknamed \u201cThe Black Knight,\u201d is missing the tip of its snout and has a fractured lower jaw.<\/p>\n \u201cIt\u2019s evidence of really energetic, violent interactions between members of the same species,\u201d Tykoski says. \u201cThe only thing that could have done this was another Tylosaurus of the same size.\u201d (Interestingly, the dinosaur T. rex also seems to have had a habit of biting each other\u2019s faces.<\/a>)<\/p>\n Inspired by a stray thought she\u2019d had looking at the Bunker mosasaur as an undergrad, Zietlow floated the name T. rex to Polcyn as a joke.<\/p>\n \u201cMike laughed really hard,\u201d she says, and agreed, noting that the name serves both to describe its anatomy and as an homage to Thurmond\u2019s suggestion from the 1960s.<\/p>\n (Teen\u00a0T. rex\u00a0or totally different dinosaur? The debate over\u00a0Nanotyrannus\u00a0gets a new twist.\u00a0<\/a>)<\/p>\n It\u2019s also not the first time a team has cheekily dubbed a non-dinosaur \u201cT. rex.\u201d In 2001, a team named an extinct prehistoric beetle trapped in amber \u201cTyrannasorus rex<\/a>,\u201d says Tom Holtz<\/a>, a vertebrate paleontologist at the University of Maryland who was not involved in the paper.<\/p>\n Since the more famous Tyrannosaurus rex and the newly discovered mosasaur did not live and hunt in the same environment, he adds, \u201cthere shouldn’t be too much confusion.\u201d For much of the 20th century, Tylosaurus was the standard mosasaur in prehistoric popular culture.<\/p>\n Indeed, if there\u2019s going to be a “T. rex of the sea”, Holtz said he\u2019s perfectly happy for it to get the name.<\/p>\n \u201cI do think it deserves it,\u201d Zeietlow says. \u201cBut we\u2019re also having a little bit of fun.\u201d<\/p>\n Asher Elbein is a freelance writer based in Austin. He regularly reports on animals, paleontology, and natural history for National Geographic<\/p>\n","protected":false},"excerpt":{"rendered":"What do you call a massive prehistoric reptilian tyrant, with large, powerful jaws and sharp serrated teeth? 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