The Talbragar Fossil Fish Bed (or Talbragar Fish Bed) is a paleontological site in New South Wales, Australia, dating to the Kimmeridgian age of the Late Jurassic. Material has been collected from the beds for over a century with the beds first being found in 1889. These beds are most likely the uppermost layer of the Purlawaugh Formation though the beds do overlie the Hawkebury Sandstone. Since being first mentioned in the literature, a number of fossil fish and plants have been described from the locality. Though not as well studied as the other groups due to most work on the beds being done at the northern site, a large number of insects have also been found. The beds themselves represent a shallow, relatively short-lived lake. During this time, the ecosystem would have been on hot and humid. The fossils were preserved due to a two-phase volcanic event with the ash from these events filling up the shallow lake.
History The Talbragar Fossil Fish Bed was first found by Arthur Lowe in 1889 with the first mention of the site in the literature being by Woodward in 1895. Charles Cullen later collecting a number of fish fossils from the site for the NSW Mines Department. These specimens would later be described by authors such as Woodward and Wade. Along with these fossil fish, a single insect would also be collected in 1968 by I. Holswich, though the preservation was more poor than what was seen in the fish. A year later, the first detailed investigation of the beds would be done by Dulhunty & Eadie who were the first to notice the eroded nature of the fish beds. Over the next two decades after this discovery, numerous other insect fossils were collected from the site representing a number of orders. Due to the site being within a paddock used for grazing on private property, not much work has been done though Lynne Bean was able to collect specimens in 2006. Over the next 5 years, a total of twenty weekend collection field trips were made resulting in over 400 insect specimens being collected. In 2021, the first tetrapod material was described from the beds; this material being a single tooth from a temnospondyl.
The name "Talbragar Fossil Fish Bed" was a general name of the site though it was put into publication as an informal name by Dulhuntly and Eadie in 1969 with this name deriving from the nearby Talbragar River.
Geology The Talbragar Fossil Fish Bed is located around north-northwest of Ulan, New South Wales and is in thickness. The unit itself is made up of sandstone and tuffaceous siltstone with the original extent of the unit being larger than what is seen today. This is due to erosion at both the northern and southern ends along with faulting present along the eastern boundary. Unweathered samples from the beds are grey and very fine grained. Within these samples, there are a number of minerals such as igneous quartz. The strata within the bed also lack a sedimentary flow structure. The Talbragar Fossil Fish Bed Reserve itself is on a slope of a hill and measures about long with its widest point being about . Originally, the fossil beds were believed to date to the late early or middle Jurassic based on the flora which correlated it with the nearby Purlawaugh Formation. However, more recent dating of the site using zircon crystals suggests that the age is more likely Kimmeridgian making the site younger than the known dating of the known Purlawaugh Formation. Even with this being the case, it has been suggested that the Talbragar Fossil Fish Bed is the upper unit of the Purlawaugh Formation. The beds themselves overlie the Hawkesbury Sandstone, a formation dating to the middle Triassic. The fish bed as a whole is divided into two sites being the northern and southern sites with the stratigraphy and biota differing between the two.
Northern Site The northern site of the Talbragar Fossil Fish Bed is where most work has been done with most of this work being done a few meters to the south of the excavations done between 2006 and 2011. Though authors originally thought that fossiliferous layers only had a thickness of , more recent work has revealed that these fossiliferous layers have a total thickness of around . LayerGeologyThicknessFossil content of the layerAWhite-yellow stained chertAbout Completely unfossiliferousBYellow-white stained, tuffaceous siltstoneUp to Mostly fish though a number of insects and plant fragments have been foundCYellow-stained sandstonePlant fragmentsDUndulating tuffaceous siltstone and medium- to course-grained sandy layers with clayballsPoorly-preserved fish
Southern Site The southern region of the Talbragar Fossil Fish Bed is not as well exposed as the northern site due to it being covered in soil and is about thick. Though separated from the northern site, the strata that is exposed is believed to be equivalent to the upper layers of the northern site. The section at the southern site is made up of tuffaceous siltstone that is more course near the base with ranges from below the surface. The fossils found in this area are within a disrupted layer of blocks with this disruption being caused by a dense forest that was present in the area in the 1800s. Below these blocks, the stratum is very finely laminated and slightly warped with very little insect and trace fossils. The basal-most layer however is very fossiliferous, containing a large amount of plant, trace, and invertebrate fossils. Unlike the northern site, the fish skeletons at the southern site are much less complete.
Fossil Composition The chemical composition of the fossils at the Talbragar Fossil Fish Bed differ from the surrounding matrix. Outside of three elements, the composition of the fish fossils are transitional between what is seen in the matrix and plant fossils. Both plant and fish fossils have specimens with what has been referred to as "dark matter" by studies. This "dark matter" is manganese infilling with the element forming dendrites in a plant fossil. Along with this, infilling is also seen in fractures and joints in fish fossils. +Type of FossilComposition compared to matrixPlantsLower amount of P, S, K, Cr, Al, Fe, Th, Mn Greater amount of SiFishLower amount of P, S, K, Cr, Al, Fe, Th, Mn, Ti Greater amount of Al, Mn, Si
Paleobiota
Actinopterygii Ray-finned fish recorded from the Talbragar Fossil Fish BedGenusSpeciesNotesImageAetheolepisA. mirabilisA dapediid with a deep body known from a single specimen with a poorly preserved head.AphnelepisA. australisAn archaeomaenid that is fusiform in shape with a maximum length of .ArchaeomaeneA. tenuisAn archaeomaenid with a rounded head and a small dorsal fin. The largest specimen from the beds is long. There was originally a second species noted within the beds (A. robustus) though the second species is now believed to represent the same species.CacatualepisC. australisA coccolepidid that was originally described as a species of Coccolepis though was later reassigned to its own genus due to a redefinition of the original genus. Within the beds, an ontogenetic series is observed with specimens measuring being found.CavenderichthysC. talbragarensisA short-faced leptolepidid ranging between in length. This fish is the most common fish taxon found within the beds.UarbryichthysU. latusAn uarbryichthyid macrosemiiform that reaches a standard length of about . Like other members of the family, it was a deep-bodied fish with a single long dorsal fin running across the length of the body.
Arachnida Arachnids recorded from the Talbragar Fossil Fish BedGenusSpeciesNotesImageTalbragaraneusT. jurassicusA potential uloborid spider identified as either a female or a juvenile individual. It would have most likely lived on vegetation on the margin of the lake.
Bivalvia Bivalves recorded from the Talbragar Fossil Fish BedGenusSpeciesNotesImageProtosphaeriumP. gianaeA sphaeriid with a short hinge. Due to the teeth of the clam being unknown, it is placed within the family due to its "pea-clam" shape and small size.
Specimens of P. talbragarensis range from in length. The hinge is this species is small in lateral profile. Specimens of P. gianae range from in length. This hinge is long and possesses a single lateral tooth.P. talbragarensis
Chondrichthyes Chondrichthyans recorded from the Talbragar Fossil Fish BedGenusSpeciesNotesImageElasmobranchii indet.An incomplete body fossil of a juvenile shark probably preserving two ventral fins and the lower lobe of the tail.
Gastropoda Gstropods recorded from the Talbragar Fossil Fish BedGenusSpeciesNotesImageProviviparusP. talbragarensisA small viviparid snail that possessed a thin operculum along with brooded embryos. This makes it so the species is the first Mesozoic member of the family to have both of these features preserved.
Insecta Insects recorded from the Talbragar Fossil Fish BedGenusSpeciesNotesImageAustroprotolindeniaA. jurassicaA protolindeniid dragonfly with a total wing length of the species is . This genus is the only member of the family present in the southern hemisphere.BeattieellusB. jurassicusAn eucnemid with a body length of . At the time of description, this genus was an oldest described member of the family.CalosargusC. talbragarensisAn archisargid fly known from a disarticulated wing measuring . Though the species is represented by a single wing, other members of the group have been suggested to be parasitic based on the presence of a long ovipositor. Similar to members of Syrphidae, these flies were most likely able to hover.EotipulaE. grangeriA small limoniid crane fly known from a body fossil measuring . It is most likely that this taxon would have lived similar to it modern relatives with males forming swarms around bodies of water.GulgongaG. beattieiA praeaulacid wasp known from a body fossil, the wings of the insect would have measured , making it a large member of the family.JuroglypholomaJ. talbragarenseA large glypholomatine rove beetle with a body length of . The elytra are smaller than other members in the subfamily with four segments of the abdomen being exposed.TalbragarocossusT. jurassicusA palaeontinid cicadomorph known from a body fossil with forewing measuring long. It differs from other earlier members of the group due to the anatomy of the forewings and the smaller size of the hindwings. More recent papers have placed this genus as a member of the 'late palaeontinidae' which have triangular forewings and smaller hindwings.TalbragarusT. averyiA nemonychid weevil with a body length (excluding the rostrum) of . Members of the family are commonly found with conifers which are one of the more common groups of plants found within the fish beds.Telmatomyia T. talbragaricaA chironomid known from seven specimens, all being pupas. These pupas are large for the family, being between long. Similar to a number of modern fly larvae, the pupa have a suction disk.ProtocharesP. brevipalpisA medium-sized hydrophilid with an oval-shaped body measuring .ProtachinusP. minorA small tachyporine rove beetle with a body length of .TalbragaropsyllidiumT. averyiA protopsyllidiid hemipteran with a slender body measuring . The genus is the most common insect within the fossil beds and is the first Jurassic member of the family to be found in Gondwana.RhopalommaR. stefaniaeAn ommatid with an elongated body measuring that would have most likely lived in rotten wood based on extant relatives. The description of this genus makes Australia the only continent with both extinct and extant members of the family.WongarooW. amplipectoraleA cerophytid beetle with a body length of . In the modern day, some members of this family live in similar, tropical environments.
Temnospondyli