The Emu Bay Shale is a

geological formation A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

Emu Bay, South Australia Emu Bay (known as Maxwell from 1882 to 1941) is a locality in the Australian state of South Australia on the north coast of Kangaroo Island located about south-west of the state capital of Adelaide and about located about west of the munici ...

, containing a major Konservat-

Lagerstätte A Lagerstätte (, from ''Lager'' 'storage, lair' '' Stätte'' 'place'; plural ''Lagerstätten'') is a sedimentary deposit that exhibits extraordinary fossils with exceptional preservation—sometimes including preserved soft tissues. These for ...

(fossil beds with soft tissue preservation). It is one of two in the world containing

Redlichiida Redlichiida is an order of trilobites, a group of extinct marine arthropods. Species assigned to the order Redlichiida are among the first trilobites to appear in the fossil record, about halfway during the Lower Cambrian. Due to the difficult ...

trilobite Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the At ...

s. The Emu Bay Shale is dated as Cambrian Series 2, Stage 4, correlated with the upper

Botomian Cambrian Stage 4 is the still unnamed fourth stage of the Cambrian and the upper stage of Cambrian Series 2. It follows Cambrian Stage 3 and lies below the Wuliuan. The lower boundary has not been formally defined by the International Commission on ...

Stage of the

Lower Cambrian The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million years ago (m ...

. Its mode of preservation is the same as the

Burgess shale The Burgess Shale is a fossil-bearing deposit exposed in the Canadian Rockies of British Columbia, Canada. It is famous for the exceptional preservation of the soft parts of its fossils. At old (middle Cambrian), it is one of the earliest foss ...

, but the larger

grain size Grain size (or particle size) is the diameter of individual grains of sediment, or the lithified particles in clastic rocks. The term may also be applied to other granular materials. This is different from the crystallite size, which refer ...

of the Emu Bay rock means that the quality of preservation is lower. More than 50 species of

s, non-biomineralized

arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...

s, palaeoscolecids, a

lobopodia The lobopodians, members of the informal group Lobopodia (from the Greek language, Greek, meaning "blunt feet"), or the formally erected phylum Lobopoda Cavalier-Smith (1998), are panarthropods with stubby legs called lobopods, a term which may ...

n, a

polychaete Polychaeta () is a paraphyletic class (biology), class of generally marine invertebrate, marine annelid worms, common name, commonly called bristle worms or polychaetes (). Each body segment has a pair of fleshy protrusions called parapodia that ...

vetulicolia VetulicoliaThe taxon name, Vetulocolia, is derived from the type genus, ''Vetulicola'', which is a compound Latin word composed of ''vetuli'' "old" and ''cola'' "inhabitant". is a taxon (either phylum or subphylum in rank) encompassing several ex ...

ns, nectocaridids,

hyoliths Hyoliths are animals with small conical shells, known as fossils from the Palaeozoic era. They are at least considered as lophotrochozoan, and possibly being lophophorates, a group which includes the brachiopods, while others consider them as be ...

brachiopod Brachiopods (), phylum Brachiopoda, are a phylum of trochozoan animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, w ...

sponge Sponges, the members of the phylum Porifera (; meaning 'pore bearer'), are a basal animal clade as a sister of the diploblasts. They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through t ...

s, chancelloriids, and a

chelicerate The subphylum Chelicerata (from New Latin, , ) constitutes one of the major subdivisions of the phylum Arthropoda. It contains the sea spiders, horseshoe crabs, and arachnids (including harvestmen, scorpions, spiders, solifuges, ticks, and mite ...

are known from the Emu Bay Shale.

Description

The Emu Bay Shale of

Kangaroo Island Kangaroo Island, also known as Karta Pintingga (literally 'Island of the Dead' in the language of the Kaurna people), is Australia's third-largest island, after Tasmania and Melville Island. It lies in the state of South Australia, southwest ...

, South Australia, is Australia's only known Burgess-Shale-type Konservat-Lagerstätte, and includes faunal elements such as ''

Anomalocaris ''Anomalocaris'' ("unlike other shrimp", or "abnormal shrimp") is an extinct genus of Radiodonta, radiodont, an Order (biology), order of early-diverging stem-group arthropods. The first fossils of ''Anomalocaris'' were discovered in the ''Ogygop ...

'', ''

Tuzoia ''Tuzoia'' (from Mount Tuzo, a mountain in the Canadian Rockies) is an extinct genus of large bivalved arthropod known from Early to Middle Cambrian marine environments from what is now North America, Australia, China, Europe and Siberia. The larg ...

'', ''

Isoxys ''Isoxys'' (meaning "equal surfaces") is a genus of extinct bivalved Cambrian arthropod; the various species of which are thought to have been freely swimming predators. It had a pair of large spherical eyes (which are the most commonly preserve ...

'', and '' Wronascolex'', in common with other Burgess-Shale-type assemblages, notably the

Chengjiang Chengjiang (; earlier Tchinkiang) is a city located in Yuxi, Yunnan Province, China, just north of Fuxian Lake. Administrative divisions Chengjiang City has 2 subdistricts and 4 townships. ;2 subdistricts * Fenglu () * Longjie () ;4 towns C ...

Biota in China, the closest palaeogeographically, although somewhat older. A few genera of non-biomineralized arthropods, among them '' Squamacula'', ''

Kangacaris ''Kangacaris'' is an extinct genus of soft-shelled trilobite-like arthropod of the nektaspid order from the Lower Cambrian (Botomian). ''K. zhangi'' is known from South Australia, and ''K. shui'' from South-West China. Etymology The generic na ...

'', and the megacheiran '' Tanglangia'', are known only from the Emu Bay Shale and Chengjiang. The site is also the source of high-quality specimens of trilobites such as ''

Redlichia takooensis ''Redlichia takooensis'' is a species of redlichiid trilobite from the lower Cambrian-aged Emu Shale of Kangaroo Island, Australia Australia, officially the Commonwealth of Australia, is a sovereign country comprising the mainland of ...

'', '' Emuella polymera'', '' Balcoracania dailyi'', '' Megapharanaspis nedini'', '' Holyoakia simpsoni'', and '' Estaingia (=Hsuaspis) bilobata''. ''

Balcoracania ''Balcoracania dailyi'' is a small (typically about ) trilobite of the family Emuellidae. Its fossils have been found in south Australia and Antarctica. It can be recognised by a short field between the front of the axis in the head (or glabella ...

'' and ''

Emuella ''Emuella'' is a genus of trilobites of the family Emuellidae. Its fossils have been found in South Australia. It can be recognised by touching glabella and frontal border, and the sub-pentagonal head, as compared to, a short field between the fr ...

'' are the only known genera of the distinctive

Redlichiina Redlichiina is a suborder of the order Redlichiida of Trilobites. The suborder contains three superfamilies: Emuelloidea, Redlichioidea and Paradoxidoidea. These trilobites are some of the oldest trilobites known. They originated at the begin ...

family

Emuellidae Emuellidae are a small family of trilobites, a group of extinct marine arthropods, that lived during the late Lower Cambrian (late Botomian) of the East Gondwana supercontinent, in what are today South-Australia and Antarctica. Emuellidae can b ...

, known for possessing the greatest number of thoracic segments known for Trilobita as a whole (a record of 103 in one ''Balcoracania'' specimen), and so far entirely restricted to Australia and Antarctica. The

sedimentary depositional environment In geology, depositional environment or sedimentary environment describes the combination of physical, chemical, and biological processes associated with the deposition of a particular type of sediment and, therefore, the rock types that will be ...

of the majority of Burgess-Shale-type assemblages is outer shelf, deeper water. The Emu Bay Shale in contrast, appears to represent deposition in restricted basins on the inner shelf, indicating that soft tissue preservation occurred in a range of environmental settings during the Cambrian. Some Emu Bay fossils display extensive mineralization of soft tissues, most often of blocky

apatite Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of OH−, F− and Cl− ions, respectively, in the crystal. The formula of the admixture of the three most common e ...

or fibrous calcium carbonate, including the oldest phosphatized muscle tissue – along with records from

Sirius Passet Sirius Passet is a Cambrian Lagerstätte in Peary Land, Greenland. The Sirius Passet Lagerstätte was named after the Sirius sledge patrol that operates in North Greenland. It comprises six places in Nansen Land, on the east shore of J.P. Koch F ...

in Greenland, the first thus far reported from the

Cambrian The Cambrian Period ( ; sometimes symbolized C with bar, Ꞓ) was the first geological period of the Paleozoic Era, and of the Phanerozoic Eon. The Cambrian lasted 53.4 million years from the end of the preceding Ediacaran Period 538.8 million ...

. Mid-gut glands are preserved three-dimensionally in calcium phosphate in the arthropods ''Isoxys'' and ''Oestokerkus'', as in related species from the Burgess Shale. The type section of the Emu Bay Shale crops out on the east side of Emu Bay where it conformably overlies the White Point Conglomerate. Here it yields a rich assemblage of ''Estaingia'', ''Redlichia'', hyolithids,

s, and the

scleritome A sclerite (Greek , ', meaning " hard") is a hardened body part. In various branches of biology the term is applied to various structures, but not as a rule to vertebrate anatomical features such as bones and teeth. Instead it refers most commonly ...

-bearing ''

Chancelloria ''Chancelloria'' is a genus of early animals known from the Middle Cambrian Burgess Shale, the Comley limestone, the Wheeler Shale, the Bright Angel Shale and elsewhere. It is named after Chancellor Peak. It was first described in 1920 by Char ...

''. At the Big Gully locality (8 km east of White Point), its presumed correlative is unconformable on the White Point Conglomerate and yields soft-bodied fossils in addition to the trilobites, including two species of the giant predator ''Anomalocaris'' (''A. briggsi'' and ''Anomalocaris'' cf. ''canadensis''), ''Isoxys'', ''Tuzoia'', two species of the nektaspid arthropod Family

Emucarididae Emucarididae is an extinct family of soft-shelled trilobite-like arthropods (nektaspids) from the Lower Cambrian of South Australia and South China. It contains only two genera – '' Emucaris'' and '' Kangacaris''. Two species were described in ...

(''

Emucaris fava ''Emucaris fava'' is an extinct species of soft-shelled trilobite-like arthropod of the nektaspid order from the Lower Cambrian (Cambrian Stage 4) of South Australia. It is the only species classified under the genus ''Emucaris''. Etymology ...

'' and '' Kangacaris zhangi''), the palaeoscolecid worm ''Wronascolex'', the problematic ''

Myoscolex ''Myoscolex'' is an early animal species known from the Cambrian Emu Bay Shale in South Australia. It was interpreted as an annelid and some supports that theory, while it was also considered as an arthropod close to '' Opabinia'', through other ...

'' and '' Vetustovermis'', and a number of rarer elements. The Big Gully trilobites rarely preserve any trace of non-biomineralized tissue; a small number of specimens of ''Redlichia'' have been reported with antennae. Taxa documented from a quarry located inland of the shoreline exposure at Big Gully include '' Oestokerkus'', a genus of leanchoiliid closely related to the well-known ''

Leanchoilia ''Leanchoilia'' is an megacheiran arthropod known from Cambrian deposits of the Burgess Shale in Canada and the Chengjiang biota of China. It was about long and had long, whip-like feelers mounted on frontal arm-like appendages. Its internal o ...

'', the early chelicerate ''

Wisangocaris ''Wisangocaris'' is an extinct genus of Cambrian arthropod known from the Emu Bay Shale of Australia. Due to the fact that trilobite fragments have been found its stomach, it was probably durophagous. It been placed in the family Sanctacarididae ...

'' and the type species of a monotypic genus of artiopodan arthropod, '' Australimicola''. An armoured lobopodian of the Family

Luolishaniidae The Luolishaniidae or Luolishaniida are a group of Cambrian and Ordovician lobopodians with anterior 5 or 6 pairs of setiferous lobopods. Most luolishaniids also have posterior lobopods each with a hooked claws, and thorn-shaped sclerites arran ...

is known from a single specimen that closely resembles an unnamed species from the Burgess Shale popularly known as Collins' Monster. In 2011, seven fossils of large, isolated

compound eye A compound eye is a visual organ found in arthropods such as insects and crustaceans. It may consist of thousands of ommatidia, which are tiny independent photoreception units that consist of a cornea, lens, and photoreceptor cells which disti ...

s were described from the inland quarry site at

Emu Bay Emu Bay may refer to *Emu Bay (South Australia), a bay ** Emu Bay, South Australia, a locality ** Emu Bay Shale, a geological formation associated with the above locality * Emu Bay (Tasmanian geographic feature), on the northwest coast ** Burnie, Ta ...

, as well as the first well-preserved visual surfaces of the eyes of ''

''. The latter specimens are consistent with anomalocaridids being closely related to

s as had been suspected. The find also indicated that advanced arthropod eyes had evolved very early, before the evolution of jointed legs or hardened exoskeletons. The eyes were 30 times more powerful than those of trilobites, long thought to have had the most advanced eyes of any species contemporary with Anomalocaris and which were only able to sense night or day. With more than 16,000 lenses, the resolution of the wide eyes would have been rivaled only by that of the modern

dragonfly A dragonfly is a flying insect belonging to the infraorder Anisoptera below the order Odonata. About 3,000 extant species of true dragonfly are known. Most are tropical, with fewer species in temperate regions. Loss of wetland habitat threate ...

, which has 28,000 lenses in each eye.Fossilised eyes of ancient super-predator found

Australian Geographic Australian Geographic is a media business that produces the ''Australian Geographic'' magazine, ''DMag'' magazine, specialist book titles, travel guides, diaries and calendars and online media. It published editions of the Australian Encyclop ...

December 9, 2011

Paleobiota

After and others

Arthropods

Other animals

References

NOTE: Much of the text of this article was used with permission of Sam Gon III from his below referenced web site, in particular from th
Emu Bay page

External links

The Palaeontology of the Lower Cambrian Emu Bay Shale
{{DEFAULTSORT:Emu Bay Shale Cambrian System of Australia Shale formations Shallow marine deposits Fossiliferous stratigraphic units of Oceania Paleontology in Australia Geology of South Australia Kangaroo Island