# Bulldog Shale

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.

## 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. 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.

## Fossil content

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

### Paleobiota
#### 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 (Theropoda) | |
| Kakuru | K. kujani | Andamooka | Opalized tibia | Now considered Tetanurae indet. | |

#### Plesiosaurs

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

#### 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. | |

#### Chondrichthyes

Chondrichthyans reported from the Bulldog Shale :
| Genus | Species | Location | Material | Notes | Images |
| Ptyktoptychion | P. eyrensis | Near Lake Eyre in northern South Australia | | | |

#### Invertebrates

Invertebratess reported from the Bulldog Shale :
| Genus | Species | Material |
| Isocrinus | I. australis | Opalised calyx |
| Maccoyella | M. barklyi | |
| Pursiphonia | P. clarkei | Opalised sponge remains |
| Tropaeum | T. imperator | |
| 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. |