tag:blogger.com,1999:blog-1953405279736337089.post6676538043729027582..comments2024-03-26T18:57:05.676-06:00Comments on The Coastal Paleontologist: New lower jaw of the extinct lipotid ParapontoporiaRobert Boesseneckerhttp://www.blogger.com/profile/04157434108254005433noreply@blogger.comBlogger8125tag:blogger.com,1999:blog-1953405279736337089.post-73847341888407378352009-11-17T18:02:30.237-07:002009-11-17T18:02:30.237-07:00Markus,
Thanks for the compliments. As far as riv...Markus,<br /><br />Thanks for the compliments. As far as river dolphins as analogues go... I wholeheartedly disagree, since many fossil platanistoids of presumably marine ecology also have long rostra; additionally, platanistoids in many phylogenies in combination with lipotids and inioids bracket different groups of extinct longirostrine odontocetes (e.g. eurhinodelphids, and kentriodontids, depending where both "groups" or parts thereof plot out). The point is that everything that these extant 'river dolphins' were related to during the Miocene also had long rostra, and that fact means that the relevancy of these extant species can't be ruled out so easily. Additionally, recall the bizarre cranial morphology of Platanista. It looks way too weird to be in the rock record. Except for Araeodelphis, and Zarchachis - both of which have bizarre maxillary crests (Araedelphis is currently under study by Stephen J. Godfrey). Both of these taxa are from marine rocks (and granted, they could be 'bloat and float'-derived fossils, but actual fluvial records (a la Potamodelphis in Florida) await discovery. Additionally, Pontoporia is distributed in the shallow marine realm. I suspect the majority of fluvial/riverine adaptations are sensory (i.e. loss of eyesight, changes in echolocation, if any; I can't recall) and physiological (although I can't recall much there, either), rather than feeding adaptations.Robert Boesseneckerhttps://www.blogger.com/profile/04157434108254005433noreply@blogger.comtag:blogger.com,1999:blog-1953405279736337089.post-58296687179552371182009-11-13T11:57:29.950-07:002009-11-13T11:57:29.950-07:00Yes, river dolphins are not really comparable to t...Yes, river dolphins are not really comparable to the extinct longirostrine forms, especially because they are so highly adapted to their environment, and show a lot of unique traits. I just mentioned them because at least some of them have very elongated jaws compared to other extant species, but are still by far exceeded in this trait by many extinct forms. <br />BTW, your drawing of the Dorudon skull looks really great!Markushttp://www.bestiarium.kryptozoologie.netnoreply@blogger.comtag:blogger.com,1999:blog-1953405279736337089.post-80432987038092681012009-11-07T18:39:03.572-07:002009-11-07T18:39:03.572-07:00I wouldn't go so far as to say that current &#...I wouldn't go so far as to say that current 'river dolphins' aren't functionally analogous to other longirostrine taxa; additionally, some analyses show quite a few of these longirostrine taxa ('platanistoids', eurhinodelphids, lipotids, iniids, pontoporiids, some kentriodontids) as stem taxa just outside or within delphinoidea, and the only 'brevirostrine' taxa in crown group delphinoidea (exceptions being Brachydelphis, and wherever the hell Delphinodon fits). This is of course discussing odontoceti diverging later than Physeterida.<br /><br />Other phylogenetic studies indicate that extant river dolphins survived due to independent adaptation to fluvial environments (can't remember the ref, but Fordyce is a coauthor), preserving the archaic nature of these early diverging members of Delphinida (and stem taxa just outside delphinida, if I remember correctly).Robert Boesseneckerhttps://www.blogger.com/profile/04157434108254005433noreply@blogger.comtag:blogger.com,1999:blog-1953405279736337089.post-63863533802852696422009-11-05T11:29:33.918-07:002009-11-05T11:29:33.918-07:00Really a great find, congratulations! Every time I...Really a great find, congratulations! Every time I see fossils or depictions of Eurhinodelphids or other extremely longsnouthed odontoceti I ask me why we don´t have a single comparable species today. Okay, river dolphins have long and very narrow jaws, at least some of the species, but they can´t rival the fossil forms. And the presence of a highly elongated snout is not such an evolutionary side issue like the super-bizarre heads of Makaracetus or Odobenocetops, but something what occured for many times among completely different animals, from fish to temnospondyls, various reptiles and even birds (to some degree at least), and for several times independetly among whales. So the question remains why such whales are no more around.Markushttp://bestiarium.kryptozoologie.netnoreply@blogger.comtag:blogger.com,1999:blog-1953405279736337089.post-65271856175076978972009-11-04T18:57:59.570-07:002009-11-04T18:57:59.570-07:00Crazy long indeed! Kinda like that skimmer porpois...Crazy long indeed! Kinda like that skimmer porpoise at the San Diego Museum.Doughttp://www.flickr.com/photos/jobarianoreply@blogger.comtag:blogger.com,1999:blog-1953405279736337089.post-36173488584549504172009-11-04T18:27:03.855-07:002009-11-04T18:27:03.855-07:00Yes, it is a veeery long symphysis! This one as fa...Yes, it is a veeery long symphysis! This one as far as I know is the most complete P. wilsoni jaw, and there is still less than half of it preserved.<br /><br />Well, go ahead and count 'em up, and we'll cowrite a post about it; I gotta read up on adaptations of long rostra and all that stuff.Robert Boesseneckerhttps://www.blogger.com/profile/04157434108254005433noreply@blogger.comtag:blogger.com,1999:blog-1953405279736337089.post-87439508170581851922009-11-02T16:25:24.375-07:002009-11-02T16:25:24.375-07:00Very nice specimen, and it sounds like quite an ad...Very nice specimen, and it sounds like quite an adventure collecting it.<br /><br />That is one crazy-long mandibular symphysis!Alton Dooleyhttp://www.paleolab.orgnoreply@blogger.comtag:blogger.com,1999:blog-1953405279736337089.post-51670957382126403322009-11-02T15:50:26.595-07:002009-11-02T15:50:26.595-07:00Nice dentary! Wow, it is amazing how much that loo...Nice dentary! Wow, it is amazing how much that looks like Lipotes, I see why it has been found to be related. <br />I bet Pomatodelphis inaequalis had more teeth. Do you want to make it a formal bet? I know P. inaequalis and Eurhinodelphis better than the west coast thugs, maybe we could really give this a try. It would be a fun way to motivate some lingering projects for me, at least.Brian Lee Beattyhttps://www.blogger.com/profile/09964393108719483799noreply@blogger.com