Early Bajocian belemnites of Southcentral Alaska: new data and new perspectives on mid-Middle Jurassic Megateuthididae and Belemnopseidae biogeography

Dzyuba, O. S.; Schraer, C D; Hults, Chad P.; Blodgett, Robert B.; Schraer, David J.

doi:10.1080/14772019.2018.1486335

Cited by 5 publications

(3 citation statements)

References 44 publications

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“…This Aalenian shift from a Toarcian Warm Mode to Aalenian–Bajocian Cool Mode ( Korte et al, 2015 ) also appears associated with a marked faunal disruption in belemnites, where random (i.e., non-morphologically-selective) extinctions lead to a distinct drop in belemnite biodiversity at least in the northwestern Peri-Tethys Ocean ( Dera, Toumoulin & de Baets, 2016 ; Neige, Weis & Fara, 2021 ). This major disruption in the evolutionary history of Jurassic belemnites ended at the Aalenian-Bajocian boundary and resulted in a radiation of the suborder Belemnopseina that partially replaced the previously dominant Belemnitina in the Western Tethys ( Weis, Mariotti & Riegraf, 2012 ; Weis, Sadki & Mariotti, 2017 ), furthermore entailing a distinct Boreal vs. Tethyan belemnite provincialism ( Doyle, 1987 ; Mariotti, Santantonio & Weis, 2007 ; Weis & Mariotti, 2007 ; Mariotti et al, 2012 ; Dzyuba et al, 2019 ). At the present state of knowledge, we can only speculate about whether faunal changes in belemnites and marine reptiles were independently impacted by the same factors, or even causally connected, since belemnites are an essential component of the food spectrum in some marine reptiles ( Massare, 1987 ; Böttcher, 1989 ; Dick, Schweigert & Maxwell, 2016 ), their faunal change could have triggered a disruption of the trophic chain up to the giant top predators.…”

Section: Discussionmentioning

confidence: 99%

Refining the marine reptile turnover at the Early–Middle Jurassic transition

Fischer

Weis

Thuy

2021

PeerJ

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Even though a handful of long-lived reptilian clades dominated Mesozoic marine ecosystems, several biotic turnovers drastically changed the taxonomic composition of these communities. A seemingly slow paced, within-geological period turnover took place across the Early–Middle Jurassic transition. This turnover saw the demise of early neoichthyosaurians, rhomaleosaurid plesiosaurians and early plesiosauroids in favour of ophthalmosaurid ichthyosaurians and cryptoclidid and pliosaurid plesiosaurians, clades that will dominate the Late Jurassic and, for two of them, the entire Early Cretaceous as well. The fossil record of this turnover is however extremely poor and this change of dominance appears to be spread across the entire middle Toarcian–Bathonian interval. We describe a series of ichthyosaurian and plesiosaurian specimens from successive geological formations in Luxembourg and Belgium that detail the evolution of marine reptile assemblages across the Early–Middle Jurassic transition within a single area, the Belgo–Luxembourgian sub-basin. These fossils reveal the continuing dominance of large rhomaleosaurid plesiosaurians, microcleidid plesiosaurians and Temnodontosaurus-like ichthyosaurians up to the latest Toarcian, indicating that the structuration of the upper tier of Western Europe marine ecosystems remained essentially constant up to the very end of the Early Jurassic. These fossils also suddenly record ophthalmosaurid ichthyosaurians and cryptoclidid plesiosaurians by the early Bajocian. These results from a geographically-restricted area provide a clearer picture of the shape of the marine reptile turnover occurring at the early–Middle Jurassic transition. This event appears restricted to the sole Aalenian stage, reducing the uncertainty of its duration, at least for ichthyosaurians and plesiosaurians, to 4 instead of 14 million years.

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Section: Discussionmentioning

confidence: 99%

Refining the marine reptile turnover at the Early–Middle Jurassic transition

Fischer

Weis

Thuy

2021

PeerJ

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“…focused on Paleozoic and Late Triassic gastropod groups (and also on other Jurassic invertebrates such as cephalopods, bivalves, belemnites and brachiopods) (Imlay 1953(Imlay , 1981(Imlay , 1982Lazar et al, 2009Lazar et al, , 2015Sandy and Blodgett, 2009;Dzyuba et al, 2018).…”

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confidence: 99%

Early Jurassic (middle Hettangian) marine gastropods from the Pogibshi Formation (Alaska) and their paleobiogeographical significance

Ferrari

Blodgett²,

Hodges

et al. 2020

andgeo

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A middle Hettangian marine gastropod assemblage is reported from the Kenai Peninsula of south-central Alaska supplying new paleontological evidence of this group in Lower Jurassic rocks of North America. Pleurotomaria pogibshiensis sp. nov. is described from the middle Hettangian marine succession informally known as Pogibshi formation, being the first occurrence of the genus in the Kenai Peninsula and the oldest occurrence of the genus in present-day Alaska and North America. One species of the genus Lithotrochus, namely Lithotrochus humboldtii (von Buch), is also reported for the first time from the Kenai Peninsula. Lithotrochus has been considered as endemic to South America for a time range from the early Sinemurian to the late Pliensbachian. The newest occurrence of Lithotrochus in rocks of the Pogibshi formation extends the paleobiogeographical and chronostratigraphical distribution of the genus into the present-day Northern Hemisphere. However, the Southern Hemisphere affinities are consistent with the hypothetical interpretations (although supported both by paleobiogeographical and paleomagnetic data) that the Peninsular terrane of south-central Alaska is far-traveled and may have originated at much more southerly paleolatitudes than its present-day position. Two other Early Jurassic caenogastropods typical of the Andean region of South America and of the Tethyan epicontinental seas are described for the first time in the Pogibshi formation, and these are Pseudomelania sp. and Pictavia sp. The new gastropod assemblage reported here shows close affinities with coeval South American and European gastropod faunas, supplying new evidence to interpret their distribution during the Early Jurassic.

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“…non-morphologically-selective) extinctions leading to a distinct drop in belemnite biodiversity at least in the northwestern Peri-Tethys Ocean (Dera, Toumoulin & de Baets, 2016;Neige, Weis & Fara, 2020). This major disruption in the evolutionary history of Jurassic belemnites ended at the Aalenian-Bajocian boundary and resulted in a radiation of the suborder Belemnopseina that partially replaced the previously dominant Belemnitina in the Western Tethys (Weis, Mariotti & Riegraf, 2012;Weis, Sadki & Mariotti, 2017), furthermore entailing a distinct Boreal vs. Tethyan belemnite provincialism (Doyle, 1987;Mariotti, Santantonio & Weis, 2007;Mariotti et al, 2012;Dzyuba et al, 2019). At the present state of knowledge, we can only speculate about whether faunal changes in belemnites and marine reptiles were independently impacted by the same factors, or even causally connected, since belemnites are an essential component of the food spectrum in some marine reptiles (Massare, 1987;Böttcher, 1989;Dick, Schweigert & Maxwell, 2016), their faunal change could have triggered a disruption of the trophic chain up to the giant top predators.…”

Section: An Abrupt Turnovermentioning

confidence: 99%

Peer Review #2 of "Refining the marine reptile turnover at the Early–Middle Jurassic transition (v0.2)"

Roberts¹

2021

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Even though a handful of long-lived reptilian clades dominated Mesozoic marine ecosystems, several biotic turnovers drastically changed the taxonomic composition of these communities. A seemingly slow paced, within-geological period turnover took place across the Early-Middle Jurassic transition. This turnover saw the demise of early neoichthyosaurians, rhomaleosaurid plesiosaurians and early plesiosauroids in favour of ophthalmosaurid ichthyosaurians and cryptoclidid and pliosaurid plesiosaurians, clades that will dominate the Late Jurassic and, for two of them, the entire Early Cretaceous as well. The fossil record of this turnover is however extremely poor, and this change of dominance appears to be spread across the entire middle Toarcian-Bathonian interval. We describe a series of ichthyosaurian and plesiosaurian specimens from successive geological formations in Luxembourg and Belgium that detail the evolution of marine reptile assemblages across the Early-Middle Jurassic transition within a single area, the Belgo-Luxembourgian sub-basin. These fossils reveal the continuing dominance of large rhomaleosaurid plesiosaurians, microcleidid plesiosaurians, and Temnodontosaurus-like ichthyosaurians up to the latest Toarcian, indicating that the structuration of the upper tier of Western Europe marine ecosystems remained essentially constant up to the very end of the Early Jurassic. These fossils also suddenly record ophthalmosaurid ichthyosaurians and cryptoclidid plesiosaurians by the early Bajocian. These results from a geographicallyrestricted area provide a clearer picture of the shape of the marine reptile turnover occurring at the early-Middle Jurassic transition. This event appears restricted to the sole Aalenian stage, reducing the uncertainty of its duration, at least for ichthyosaurians and plesiosaurians, to 4 instead of 14 million years.

show abstract

Early Bajocian belemnites of Southcentral Alaska: new data and new perspectives on mid-Middle Jurassic Megateuthididae and Belemnopseidae biogeography

Cited by 5 publications

References 44 publications

Refining the marine reptile turnover at the Early–Middle Jurassic transition

Refining the marine reptile turnover at the Early–Middle Jurassic transition

Early Jurassic (middle Hettangian) marine gastropods from the Pogibshi Formation (Alaska) and their paleobiogeographical significance

Peer Review #2 of "Refining the marine reptile turnover at the Early–Middle Jurassic transition (v0.2)"

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