"Long before it's in the papers"
January 27, 2015


When humans were smaller, and crocs much bigger

May 9, 2012
Courtesy of the The University of Iowa
and World Science staff

Al­though di­no­saurs nev­er co­existed with hu­ma­ns, may­be they did­n’t need to. Re­search sug­gests an­oth­er rep­tilian mon­ster was on hand to scare the liv­ing day­lights out of early hu­ma­ns or their kin: a croc­o­dile whose shoul­ders easily came up to the height of an av­er­age ma­n’s el­bows at the time.

Dubbed Crocody­lus thor­b­jar­nar­soni, the beast is “the larg­est known true croc­o­dile” in our plan­et’s his­tory, said Uni­vers­ity of Io­wa geo­sci­en­tist Chris­to­pher Brochu, whose re­search on it is pub­lished in the May 3 is­sue of the Jour­nal of Ver­te­bra­te Pa­le­on­tol­ogy. “It may have ex­ceeded 27 feet [8.2 me­ters] in length. By com­par­i­son, the larg­est rec­orded Nile croc­o­dile was less than 21 feet, and most are much small­er.”

“We don’t ac­tu­ally have fos­sil hu­man re­mains with croc bites,” he said. “But the crocs were big­ger than to­day’s croc­o­diles, and we were smaller, so there probably was­n’t much bit­ing in­volved”—the pro­cess was prob­ably mainly a mat­ter of swal­low­ing.

A di­a­gram show­ing the rel­a­tive sizes of an­cient and mod­ern crocodiles (large and small, re­spec­tive­ly) and an­cient and mod­ern hu­mans (small and large, re­spec­tive­ly.) The black line marks a length of a me­ter (3 feet 3 inches). (Il­lus­tra­tion by Chris Bro­chu)

Brochu’s pa­per de­scribes the an­i­mal as a newly iden­ti­fied spe­cies, though the ex­ist­ence of the crea­ture it­self is­n’t news. Fos­sils have been avail­a­ble at Na­t­ional Mu­se­um of Ken­ya in Nai­ro­bi, but were thought to be un­usu­ally large mem­bers of the mod­ern Nile croc­o­dile spe­cies, he ex­plained. “We really don’t know where the Nile croc­o­dile came from,” he said, “but it only ap­pears af­ter some of these pre­his­tor­ic gi­ants died out.”

The beast lived be­tween two mil­lion and four mil­lion years ago in Ken­ya, added Brochu, who iden­ti­fied it as a new spe­cies based on the Na­t­ional Mu­se­um fos­sils. Some of these were found at sites known for ma­jor fos­sil dis­cov­er­ies of hu­man an­ces­tors, he added, so “it lived along­side our an­ces­tors, and it probably ate them.” Early man had no plumb­ing and would have had to seek out wa­ter the same place oth­er an­i­mals did—at riv­ers and lakes, right where crocs lie in wait.

He added that al­though the fos­sils con­tain no ev­i­dence of hu­ma­n-rep­tile en­coun­ters, croc­o­diles gen­er­ally eat wha­tever they can swal­low, and hu­ma­ns of that time pe­ri­od would have stood no more than four feet (1.2 me­ters) tall. Pre­his­tor­ic hu­ma­ns or rel­a­tives liv­ing at the time in­clud­ed the ape-like Aus­tra­lo­pithecus africanus and the more hu­ma­n-like Ho­mo ha­bilis, which ap­pears la­ter, start­ing about 2.5 mil­lion years ago in the fos­sil rec­ord.

It took four men—mod­ern ones—just to lift a fos­sil skull of C. thor­b­jar­nar­soni, Brochu said. He named the spe­cies is hon­or of his col­league John Thor­b­jar­nar­son, a ma­jor croc­o­dile au­thor­ity who died of ma­lar­ia in the field sev­er­al years ago. “He was a gi­ant in the field, so it only made sense to name a gi­ant af­ter him,” Brochu said. 

This is­n’t the first find­ing from Brochu in­volv­ing an­cient cro­co­diles. In 2010, he pub­lished a pa­per on a man-eating horned croc­o­dile from Tan­za­nia named Croc­ody­lus an­thro­poph­a­gus, a rel­a­tive of the ani­mal fea­tured in his new work.

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Although dinosaurs never co-existed with humans, maybe they didn’t need to, new research suggests. Another immense reptile was on hand to scare the living daylights out of early humans or their kin: a crocodile whose shoulders easily came up to the height of an average man’s elbows at the time. Dubbed Crocodylus thorbjarnarsoni, the beast is “the largest known true crocodile” in the planetsaid University of Iowa geoscientist Christopher Brochu, whose research on it is published in the May 3 issue of the Journal of Vertebrate Paleontology. “It may have exceeded 27 feet [8.2 meters] in length. By comparison, the largest recorded Nile crocodile was less than 21 feet, and most are much smaller.” “We don’t actually have fossil human remains with croc bites, but the crocs were bigger than today’s crocodiles, and we were smaller, so there probably wasn’t much biting involved,” he added. With this monster, named Crocodylus thorbjarnarsoni, the process was probably more a matter of swallowing than biting, he said. Brochu’s paper describes the animal as a newly identified species, though the existence of the creature itself isn’t news. Fossils have been available at National Museum of Kenya in Nairobi, but were thought to be unusually large members of the modern Nile crocodile species, he explained. “We really don’t know where the Nile crocodile came from,” he said, “but it only appears after some of these prehistoric giants died out.” The beast lived between two and four million years ago in Kenya, added Brochu, who identified it as a new species based on the National Museum fossils. Some of these were found at sites known for major fossil discoveries of human ancestors, he added, so “it lived alongside our ancestors, and it probably ate them.” Early man had no plumbing and would have had to seek out water the same place other animals did—at rivers and lakes, right where crocs lie in wait. He added that although the fossils contain no evidence of human-reptile encounters, crocodiles generally eat whatever they can swallow, and humans of that time period would have stood no more than four feet (1.2 meters) tall. Prehistoric humans or relatives living at the time included the ape-like Australopithecus africanus and the more human-like Homo habilis, which appears later, starting about 2.5 million years ago in the fossil record. It took four men—modern ones—just to lift a fossil skull of Crocodylus thorbjarnarsoni, Brochu said. He named the species is honor of his colleague John Thorbjarnarson, a major crocodile authority who died of malaria in the field several years ago. “He was a giant in the field, so it only made sense to name a giant after him,” Brochu said. This isn’t the first finding from Brochu involving eastern African fossils. In 2010, he published a paper on his finding a man-eating horned crocodile from Tanzania named Crocodylus anthropophagus—a relative of the croc featured in his new work.