Siderops kehli was a large temnospondyl amphibian from Queensland, Australia. Its holotype preserves an articulated skull and mandible together with much of the postcranial skeleton, including vertebrae, ribs, girdles and limbs. This unusually complete material supports a more detailed reconstruction than is possible for many fossil amphibians. Revised dating places the enclosing deposits in the Early Jurassic, making Siderops a distinctive member of the ancient amphibian catalogue.
Quick facts
| Species | Siderops kehli |
|---|---|
| Group | Temnospondyli; Chigutisauridae |
| Age | Early Jurassic; enclosing deposits no older than 176.6 ± 2 Ma |
| Formation | Evergreen Formation, Queensland |
| Holotype | QM F7882, skull and much of the skeleton |
| Size | Large; estimates exceed 2.5 m, with some museum accounts saying over 3 m |
| In the catalogue | Ancient amphibians |
What the fossils establish
The preserved elements include much of the vertebral column, ribs, girdles and limbs. Missing or damaged areas still require reconstruction.
This date constrains sediment deposition and means the beds are no older than the dated material; it is not a direct date of the animal’s death.
Total length is reconstructed. The fossil supports a large animal, but published summaries use different approximate figures.
No fossil preserves a hunt or a specific meal. Fish are plausible prey in the setting, but diet details remain inferred.
A remarkable Australian skeleton
Siderops kehli is known from the Evergreen Formation of Queensland. The holotype, QM F7882, was recovered in the Wandoan region and is held by the Queensland Museum. Unlike genera known mainly from isolated skull fragments, this specimen preserves an articulated skull and lower jaws as well as a substantial part of the body behind them.
The skeleton includes much of the vertebral column, ribs, shoulder and pelvic girdles, and elements of the forelimbs and hindlimbs. The bones are not all equally complete, and some portions are missing, but their association allows researchers to connect cranial anatomy with the rest of the body. A 2023 checklist of Australian Mesozoic tetrapods recognizes this unusual completeness as a central feature of the specimen.
The type area is near Kolane Station, around sixty kilometres north of Wandoan. The fossil was collected from sedimentary rocks that record an ancient water-rich landscape. The setting helps frame the animal’s ecology, but the exact place where it died may differ from the place where it lived because water can transport carcasses or bones.
Dating the enclosing rocks
Earlier accounts broadly placed the fossil in the Early Jurassic. A later geochronological study reported a maximum depositional age of 176.6 ± 2 million years for sediment associated with the occurrence. A maximum depositional age is a constraint: the deposit cannot be older than the youngest dated grains used in the analysis. It is not a direct measurement of the animal’s lifespan or the precise day it was buried.
The date refines the geological framework and helps compare the Australian fauna with other Jurassic assemblages. It should not be quoted as though a laboratory dated the fossil bone itself. The animal lived before the sediment finally accumulated around its remains, and the difference may be small or substantial depending on the history of the grains and the deposit.
Geological age estimates can also change as dating methods and regional correlations improve. The secure statement is that Siderops came from the Early Jurassic Evergreen Formation and that the enclosing strata have a reported maximum age constraint near 176.6 million years. Narrower claims need to specify which beds and dating method they refer to.
Skull, size and predatory interpretation
The broad skull and powerful jaws identify a large predatory temnospondyl. The articulated lower jaw makes the arrangement of the mouth easier to assess than it would be from isolated bones. The postcranial skeleton indicates a substantial-bodied animal with limbs and a long trunk. These features support a reconstruction of a large aquatic or semi-aquatic hunter.
Published size estimates are approximate. The Russian source describes an animal more than 2.5 metres long, while Queensland Museum and state summaries commonly describe it as over 3 metres. Neither is a direct tape measurement of an intact skeleton. The difference reflects how incomplete regions are restored and how total length is estimated. It is best to call Siderops large and state that reconstructions exceed 2.5 metres, with some institutional accounts giving a figure above 3 metres.
Fish are plausible prey for a large aquatic predator, but there is no preserved stomach content that confirms a particular meal. The skull is consistent with seizing prey; it does not record a specific strike or prove that every individual hunted in the same way. A quiet river or lake scene is an informed reconstruction from the fossils and geology.
What a complete-looking reconstruction still adds
The holotype is unusually informative, but it is not a complete record of muscles, cartilage, skin or colour. Some bones are incomplete and external soft tissues are absent. A picture can show the documented skull and the broad body plan, while details such as skin folds, exact limb posture and colour pattern are interpretive.
Siderops demonstrates that temnospondyl amphibians persisted well into the Jurassic in Australia. Its associated skeleton connects anatomical features that are separated in many other genera, and modern dating sharpens the setting. The precise total length, diet and hunting behaviour remain less certain. For comparison with another aquatic temnospondyl, see Mastodonsaurus; the broad-headed Triassic Plagiosternum represents a different specialized form.
Frequently asked questions
How complete is the Siderops fossil?
The holotype preserves an articulated skull and jaws plus much of the vertebral column, ribs, girdles and limbs, though some elements are incomplete or absent.
How old is it?
It is Early Jurassic. A study reported a maximum depositional age of 176.6 ± 2 million years for associated sediment; this is a constraint on the rock, not a direct date of the animal.
How long was Siderops?
It was large. Estimates exceed 2.5 metres, while some museum summaries say over 3 metres; total length is reconstructed from incomplete remains.
What did it eat?
It was a large predator and fish are plausible prey, but no stomach contents establish a specific diet.