Wikipedia:Reference desk/Archives/Science/2022 December 27

= December 27 =

Late Cretaceous American Interchange: Where is the Smoking Gun?
How is there any proof that there was an actual american biotic interchange between South American fauna and North American fauna during the late Cretaceous? keep in mind that the american biotic interchange that started during the Piacenzian had terror birds, glyptodonts, megalonychid ground sloths, megatheriid ground sloths, nothrotheriid ground sloths, toxodontids, new world porcupines cross over from South America into North America while gomphotheres, dire wolves, sabertooth cats, spectacled bears, jaguars, cougars, camelids, white-tailed deer, marsh deer crossed over from North America into South America, so if there was an actual american biotic interchange during the late Cretaceous, why is there no evidence of animals like abelisaurs, megaraptorans, noasaurids, elasmarians, notosuchians, unenlagiinae unenlagiids crossing over from South America into North America and animals like lambeosaurine hadrosaurs, edmontosaurini hadrosaurs, chasmosaurine ceratopsids, centrosaurine ceratopsids, tyrannosaurids, eudromaeosaurs crossing over from North America into South America? CuddleKing1993 (talk) 09:09, 27 December 2022 (UTC)
 * The animals that you list as crossing between North and South America all lived many millions of years after the end of the Cretaceous. CodeTalker (talk) 03:52, 28 December 2022 (UTC)
 * The OP wrote that these animals crossed during the Piacenzian (in the Great American Biotic Interchange, using the Panamanian land bridge that formed during that age). The question – as I interpret it – is, why didn't a similar exchange take place during the late Cretaceous? The tragic fact of the matter is, as was pointed out to the OP before, in the late Cretaceous, North America was not connected to South America. --Lambiam 07:57, 28 December 2022 (UTC)
 * So why did apparently kritosaurini hadrosaurs and nodosaurs cross over into South America? CuddleKing1993 (talk) 11:16, 28 December 2022 (UTC)
 * To repeat myself from 11 days ago in response to an earlier question "according to this paper there was probably a link between North and South America during the Campanian (Late?), via a line of volcanic islands, allowing "a dispersal route for hadrosaurids and other vertebrates"." Mikenorton (talk) 14:18, 28 December 2022 (UTC)
 * Then why did only kritosaurini hadrosaurs and nodosaurs disperse into South America? CuddleKing1993 (talk) 20:30, 28 December 2022 (UTC)
 * Maybe some of them couldn't swim? Maybe all of them could swim, but the inter-island seas were hazardous and only the two you mention were lucky enough to make it all the way? Maybe some that made it part of the way were then wiped out by volcanic eruptions? If you haven't found the answer in peer-reviewed literature, then almost certainly no-one knows. Maybe future discoveries will allow someone to figure it out, in a century or two from now. Maybe we'll never know: Paleontology is like that. {The poster formerly known as 87.81.230.195} 51.194.245.235 (talk) 12:34, 29 December 2022 (UTC)