Squalicorax Age.

[Triceratops]

On some sites I have read that the genus of shark squalicorax lived only in the cretaceous. On others I've read that it was still alive in the Eocene. Did it survive the K.P extinction or did it die out with the dinosaurs(And all the other interesting animals ) I would love to know!

Thanks.

Edited August 22, 2014 by Triceratops

[non-remanié]

apparently squalicorax was too specialized to survive the K/Pg event.

[Triceratops]

Thanks.:-)

Edited August 23, 2014 by Triceratops

[painshill]

Perhaps not all Squalicorax were specialized. Extinction rates were heavy for sharks in general.

You may be interested in this abstract from “Neoselachian (Chondrichthyes, Elasmobranchii) diversity across the Cretaceous–Tertiary boundary”: Jurgen Kriwet, Michael J. Benton [Palaeogeography, Palaeoclimatology, Palaeoecology 214 (2004) 181– 194]

Fishes are often thought to have passed through mass extinctions, including the Cretaceous–Tertiary (KT) event, relatively unscathed. We show that neoselachian sharks suffered a major extinction at the K/T boundary. Out of 41 families, 7 became extinct (17+/-12%). The proportional measure increases at lower taxic levels: 56+/-10% loss of genera (loss of 60 out of 107) and 84+/-5% loss of species (loss of 182 out of 216). However, the Maastrichtian and Danian are characterized by a high number of singleton taxa. Excluding singletons we have calculated a 34+/-11% loss of genera and a 45+/-9% loss of species. The simple completeness metric (SCM) for genera displays a decrease from the Maastrichtian (94%) to the Danian (85%) indicating a rather complete fossil record of neoselachian genera. The extinctions were heavy among both sharks and batoids (skates and rays), but most severe among batoids, which lost almost all identifiable species. There were equal losses among open marine apexpredators (loss of Anacoracidae, Cretoxyrhinidae, and Scapanorhynchidae) and durophagous demersal forms from the continental shelf and shallow seas (Hypsobatidae, Parapaleobatidae, Sclerorhynchidae, Rhombodontidae). Benthopelagic and deep-sea forms were apparently little affected. New families with similar ecological roles (Carcharhinidae, Isuridae, Torpedinidae) replaced these families in the Danian, and full diversity of the different shark and batoid groups had been recovered by the end of the Paleocene or early Eocene. Sharks and rays suffered levels of extinction entirely in line with other groups of organisms at the K/T extinction event.

And from within the paper:

Ideally, the diversity pattern of aquatic vertebrates such as actinopterygians and selachians across the K/T boundary follows that of other organisms resulting in high extinction rates. For instance, the effect of the K/T boundary event on actinopterygians is rather similar to that of neoselachians with 19% of families becoming extinct (Cavin, 2001). However, mainly specialized forms were affected (Cavin and Martin, 1995; Cavin, 2001). Previous works on neoselachians suggest, conversely, mass extinction of taxa at the end of the Cretaceous although the rates differ significantly between studies….

….A number of pelagic apex predators such as Archaeolamna, Paranomotodon, Squalicorax, Cretoxyrhina, and Scapanorhynchus disappeared at the end of the Cretaceous…. These are medium- to large-sized and mostly fast-swimming predators of the epipelagic and shelf zones with generally rather broad-spectrum diets. However, there are indications that at least several species of Squalicorax and Cretoxyrhina possibly were considerably specialized (e.g., Schwimmer et al., 1997; Shimada, 1997, 2000). These top predators becoming extinct at the end of the Cretaceous were replaced by other pelagic groups with similar adaptations in the Danian (Carcharhinidae, Isuridae) although extinction and origination rates are not balanced.

Edited August 24, 2014 by painshill

[siteseer]

Cretoxyrhina is not known to have survived into the Early Maastrichtian and I'm not sure that Paranomotodon did either. Also, I'm not aware of a Danian isurid except for the species Isurus schoutedeni though that one has been assigned to Cretalamna by at least a couple of researchers (not much written about that one).

Perhaps not all Squalicorax were specialized. Extinction rates were heavy for sharks in general.

You may be interested in this abstract from “Neoselachian (Chondrichthyes, Elasmobranchii) diversity across the Cretaceous–Tertiary boundary”: Jurgen Kriwet, Michael J. Benton [Palaeogeography, Palaeoclimatology, Palaeoecology 214 (2004) 181– 194]

Fishes are often thought to have passed through mass extinctions, including the Cretaceous–Tertiary (KT) event, relatively unscathed. We show that neoselachian sharks suffered a major extinction at the K/T boundary. Out of 41 families, 7 became extinct (17+/-12%). The proportional measure increases at lower taxic levels: 56+/-10% loss of genera (loss of 60 out of 107) and 84+/-5% loss of species (loss of 182 out of 216). However, the Maastrichtian and Danian are characterized by a high number of singleton taxa. Excluding singletons we have calculated a 34+/-11% loss of genera and a 45+/-9% loss of species. The simple completeness metric (SCM) for genera displays a decrease from the Maastrichtian (94%) to the Danian (85%) indicating a rather complete fossil record of neoselachian genera. The extinctions were heavy among both sharks and batoids (skates and rays), but most severe among batoids, which lost almost all identifiable species. There were equal losses among open marine apexpredators (loss of Anacoracidae, Cretoxyrhinidae, and Scapanorhynchidae) and durophagous demersal forms from the continental shelf and shallow seas (Hypsobatidae, Parapaleobatidae, Sclerorhynchidae, Rhombodontidae). Benthopelagic and deep-sea forms were apparently little affected. New families with similar ecological roles (Carcharhinidae, Isuridae, Torpedinidae) replaced these families in the Danian, and full diversity of the different shark and batoid groups had been recovered by the end of the Paleocene or early Eocene. Sharks and rays suffered levels of extinction entirely in line with other groups of organisms at the K/T extinction event.

And from within the paper:

Ideally, the diversity pattern of aquatic vertebrates such as actinopterygians and selachians across the K/T boundary follows that of other organisms resulting in high extinction rates. For instance, the effect of the K/T boundary event on actinopterygians is rather similar to that of neoselachians with 19% of families becoming extinct (Cavin, 2001). However, mainly specialized forms were affected (Cavin and Martin, 1995; Cavin, 2001). Previous works on neoselachians suggest, conversely, mass extinction of taxa at the end of the Cretaceous although the rates differ significantly between studies….

….A number of pelagic apex predators such as Archaeolamna, Paranomotodon, Squalicorax, Cretoxyrhina, and Scapanorhynchus disappeared at the end of the Cretaceous…. These are medium- to large-sized and mostly fast-swimming predators of the epipelagic and shelf zones with generally rather broad-spectrum diets. However, there are indications that at least several species of Squalicorax and Cretoxyrhina possibly were considerably specialized (e.g., Schwimmer et al., 1997; Shimada, 1997, 2000). These top predators becoming extinct at the end of the Cretaceous were replaced by other pelagic groups with similar adaptations in the Danian (Carcharhinidae, Isuridae) although extinction and origination rates are not balanced.

[non-remanié]

Very true! I would think that Cretoxyrhina and Paranomotodon should have been fairly easy to confirm did not survive much into the Maastrichtian. But I think a lack of good Maastrichtian and definitelyt mid-late Maastrichtian faunas might make this a little difficult.

Cretoxyrhina is not known to have survived into the Early Maastrichtian and I'm not sure that Paranomotodon did either. Also, I'm not aware of a Danian isurid except for the species Isurus schoutedeni though that one has been assigned to Cretalamna by at least a couple of researchers (not much written about that one).

[Triceratops]

Thanks for your helpfull reply's.

Edited September 8, 2014 by Triceratops