Bulldog Shale

Bulldog Shale
Stratigraphic range: Aptian-Albian
~120–110 Ma

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Bulldog Shale; Stratigraphic range: Aptian-Albian; ~120–110 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
Unit of	Rolling Downs Group; Marree Subgroup
Sub-units	Wilpoorinna Breccia Member
Underlies	Coorikiana Sandstone
Overlies	Cadna-owie Formation
Thickness	200–340 m (660–1,120 ft)
Lithology
Primary	Mudstone, claystone
Other	Shale, limestone, gypsum
Location
Coordinates	30.5°S 137.2°E
Approximate paleocoordinates	67.5°S 104.5°E
Region	South Australia
Country	Australia
Extent	Eromanga Basin
	Bulldog Shale (Australia) Bulldog Shale (South Australia)

The Bulldog Shale is a formation of Early Cretaceous age (Aptian to Albian stages) that forms part of the Marree Subgroup of the Rolling Downs Group, located in the Eromanga Basin of South Australia, Queensland and New South Wales.[1][2]

Description

It is the lowermost unit in the Marree Subgroup, overlying the Cadna-owie Formation and is overlain by the Coorikiana Sandstone. The formation dates to the Aptian to Albian stages of the Early Cretaceous.[3] The Bulldog Shale is composed of finely laminated carbonaceous and pyritic mudstone and claystone beds. Weathering has caused heavy leaching and bleaching in some regions of the Bulldog Shale, including those around Coober Pedy, so that the rocks are white or multicolored. These horizons contain rich opal deposits. Horizons without this bleaching are primarily composed of organic-rich shale. Gypsum, in addition to carbonate limestone concretions rich in fossils are common in these unbleached shaly horizons.[4]

Fossil content

The Bulldog Shale has yielded fossils of plants, invertebrates, fish, and reptiles.[5] The macroinvertebrate fauna of this formation includes several molluscs, such belemnites, gastropods, and bivalves. Fish are represented by chimaeras[6] and ray-finned fish (these include teleosts)[6] and a lungfish. Sharks are conspicuously absent in the Bulldog Shale.[4] Many plesiosaurs are known from the formation, including leptocleidids, elasmosaurids,[4] pliosaurids, and possible polycotylids. Ichthyosaurs are also present.[7] Archosaur fossils from the Bulldog Shale are rare, and are represented mostly indeterminate specimens, some of which can be assigned to Dinosauria.[8] Due to the coastal location of the Bulldog Shale, large amounts of wood have also been recovered in this formation.[4]

Archosaurs

Archosaurs reported from the Bulldog Shale
Genus	Species	Location	Material	Notes	Images
Archosauria	Indet.	Andamooka, Coober Pedy	Various fragments, some opalized	Includes some material referable to Dinosauria[8]
Kakuru	K. kujani	Andamooka	Opalized tibia	Now considered Tetanurae indet.[8]

Plesiosaurs

Plesiosaurs reported from the Bulldog Shale
Genus	Species	Location	Material	Notes	Images
Kronosaurus	K. queenslandicus		Teeth	Originally referred to cf. K. sp.[4][7]
Leptocleidus	L. sp.			Reclassified as Umoonasaurus[7]
Opallionectes	O. andamookaensis	Lunatic Hill opal field	Opalized incomplete articulated skeleton	A plesiosaur of uncertain classification[4][7]
Umoonasaurus	U. demoscyllus	Zorba Extension Opal Field, Andamooka opal fields, Curdimurka area, Neales River region	Opalized skulls and skeletons	A small leptocleidid[9] plesiosaur with three crests on its head[2]
Elasmosauridae	Indet.	Andamooka	Partial skeletons and several fragments	[4]
Polycotylidae	Indet.	Hermit Hill	Fragmentary specimen	[4]

Ichthyosaurs

Ichthyosaurs reported from the Bulldog Shale
Genus	Species	Location	Material	Notes	Images
Platypterygius	P. sp.	Bopeechee Siding	Fragmentary cranial and postcranial material	The specimen SAM P14508 shows evidence of healed bite marks.[5]

Chondrichthyes

Chondrichthyans reported from the Bulldog Shale
Genus	Species	Location	Material	Notes	Images
Edaphodon	E. eyrensis

Color key

Taxon	Reclassified taxon	Taxon falsely reported as present	Dubious taxon or junior synonym	Ichnotaxon	Ootaxon	Morphotaxon

Notes
Uncertain or tentative taxa are in small text; ~~crossed out~~ taxa are discredited.

References

Geoscience Australia. "Stratigraphic Unit Details: Bulldog Shale". Australian Stratigraphic Units Database. Retrieved 26 June 2020.
Kear, Benjamin P.; Schroeder, Natalie I.; Lee, Michael S.Y. (2006). "An archaic crested plesiosaur in opal from the Lower Cretaceous high-latitude deposits of Australia". Biology Letters. 2 (4): 615–619. doi:10.1098/rsbl.2006.0504. PMC 1833998. PMID 17148303.
Bulldog Shale at Fossilworks.org
Kear, Benjamin P. (2006). "Marine reptiles from the Lower Cretaceous of South Australia: elements of a high‐latitude cold‐water assemblage". Palaeontology. 49 (4): 837–856.
Zammit, Maria; Kear, Benjamin P. (2011). "Healed bite marks on a Cretaceous ichthyosaur" (PDF). Acta Palaeontologica Polonica. 56 (4): 859–863. doi:10.4202/app.2010.0117.
McHenry, Colin R. (2009). Devourer of Gods: The palaeoecology of the Cretaceous pliosaur Kronosaurus queenslandicus (Thesis). The University of Newcastle.
Kear, Benjamin P. (2016). "Cretaceous marine amniotes of Australia: perspectives on a decade of new research" (PDF). Memoirs of Museum Victoria. 74: 17–28. doi:10.24199/j.mmv.2016.74.03.
Barrett, Paul M.; Kear, Benjamin P.; Benson, Roger B.J. (2010). "Opalized archosaur remains from the Bulldog Shale (Aptian: Lower Cretaceous) of South Australia" (PDF). Alcheringa. 34: 1–9. ISSN 0311-5518.
Parrilla-Bel, Jara; Canudo, José Ignacio (2015). "On the presence of plesiosaurs in the Blesa Formation (Barremian) in Teruel (Spain)". Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen. 278 (2): 213–227. doi:10.1127/njgpa/2015/0526.