| Savannasaurus | |
|---|---|
 | |
| Skeletal diagram and selected fossils | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | Saurischia |
| Clade: | †Sauropodomorpha |
| Clade: | †Sauropoda |
| Clade: | †Macronaria |
| Genus: | †Savannasaurus Poropatet al. 2016 |
| Species: | †S. elliottorum |
| Binomial name | |
| †Savannasaurus elliottorum Poropatet al. 2016 | |
Savannasaurus is a genus oftitanosauriansauropod dinosaur from theLate CretaceousWinton Formation ofQueensland,Australia. It contains one species,Savannasaurus elliottorum, named in 2016 by Stephen Poropat and colleagues. Theholotype and only known specimen, originally nicknamed "Wade", is the most complete specimen of an Australian sauropod, and is held at theAustralian Age of Dinosaurs museum. Dinosaurs known from contemporary rocks include its close relativeDiamantinasaurus and thetheropodAustralovenator; associated teeth suggest thatAustralovenator may have fed on the holotype specimen.
At 15 metres (49 ft) long,Savannasaurus was a medium-sized titanosaur. It is notable for its wide hips, which would have been over 1.1 metres (3 ft 7 in) wide at their widest points. This would have distributed its body weight more evenly, along with a robusthumerus (upper arm bones) and possibly also the tallastragalus (ankle bone). Combined with a flexible vertebral column, these traits would have madeSavannasaurus better at navigating the muddy ground of thefloodplains that it lived on. Other titanosaur lineages also show some of these traits, which might have been independently acquired from similar environmental pressures.
Various traits suggest thatSavannasaurus was an early-diverging (orbasal) member of the Titanosauria, but not a member of the more specialized groupLithostrotia. Among these are the absence ofhyposphene-hypantrum articulations in its vertebrae, which was one of the flexibility-enhancing traits that may have appeared in multiple titanosaur lineages.Palaeobiogeographic analyses suggest that the ancestors ofSavannasaurus andDiamantinasaurus were from either Asia or one of the southernGondwanan continents; regardless, they likely migrated to Australia through Antarctica around 105–100 million years ago.
In March 2005, the first specimen ofSavannasaurus was discovered by David Elliot, founder ofAustralian Age of Dinosaurs (AODF), along with his wife Judy and their children. The specimen, now catalogued as AODF 660, was found on the Belmont sheep station, 60 kilometres (37 mi) northeast ofWinton, Queensland; the site was given the number AODF 82, and is informally called the "Ho-Hum site".[1] Excavations by theQueensland Museum and hundreds of volunteers unearthed the specimen in July and September of that year. Asiltstoneconcretion containing the specimen was split alonggypsum-filled fractures using jackhammers and chisels, with the pieces being marked to facilitate reassembly.Preparation of the specimen took around a decade,[2] with air scribes and micro-jacks being used. Adhesives, such assuperglue andaraldite, were then used to put the pieces back together. The marks allowed the orientation of the specimen as it was found to be reconstructed, which informed a three-dimensional site map constructed withphotogrammetry.[3]
AODF 660 consists of around 40 bones: onecervical (neck), the third through tenthdorsal (trunk), at least foursacral (hip), and at least fivecaudal (tail)vertebrae; cervical and (fragmentary) dorsal ribs; portions of the shoulder girdle, including a fragmentaryscapula, a leftcoracoid, and bothsternal plates; parts of the forelimbs, including portions of bothhumeri, a fragmentaryulna, the leftradius, and hand bones (the left first to fifthmetacarpals, the right fourth metacarpal, and twophalanges); the fused hip bones, namely both the left and the rightpubis andischium; foot bones (the leftastragalus and right thirdmetatarsal); and other fragments.[1] One of the foot bones was originally thought to have belonged to a theropod,[4] while the metacarpals were initially also interpreted as having come from the opposite hands.[3] The specimen is the most complete sauropod specimen known from Australia, and represents approximately 20% to 25% of the animal.[2]
The bones were preserved over an area of less than 20 m2 (220 sq ft). While the dorsal vertebrae were not articulated, they were preserved in sequence in front of the hip bones, allowing for their identification. The ribs on the left side appear to have been crushed prior to fossilization, before all of them were fragmented further. The fifth dorsal vertebra and both humeri show signs of being trampled by other dinosaurs before fossilization, which may also explain the scattered bones; however, the bones were less scattered than other dinosaur specimens from contemporary rocks. A third excavation in September 2006 discovered no additional remains, but a partialcentrum from a caudal vertebra was found on the surface in 2013.[3]
Having been nicknamed "Wade",[2] AODF 660 was formally described and named in 2016 by Stephen Poropat and colleagues in a paper that also described a skull belonging toDiamantinasaurus. They identified AODF 660 as theholotype of a new genus and species,Savannasaurus elliottorum; the generic name ofSavannasaurus, fromTaínozavana (the root of the word "savanna"), refers to the environment in which it was found, while the specific nameelliottorum honours the Elliott family and their contributions to Australian palaeontology.[1] The preliminary anatomical description of AODF 660 in this paper was supplemented in 2020 by another paper from many of the same authors, which provided a full description of itsosteology.[3]
Savannasaurus was a medium-sizedtitanosaur that measured about 15 metres (49 ft) in length, with a weight of around 20 tonnes (22 short tons) and a shoulder height of around 3 metres (9.8 ft).[4]
As with most other members of theTitanosauriformes, the vertebrae ofSavannasaurus were camellate, orpneumatized by small holes created by air sacs, and they lackedhyposphene-hypantrum articulations that allowed neighbouring vertebrae to interlock. The cervical and dorsal vertebrae ofSavannasaurus were allopisthocoelous, or having a centrum (vertebral body) that is convex in front and concave behind. All other members ofEusauropoda have opisthocoelous cervicals, and all other members ofMacronaria have opisthocoelous dorsals.[1] Unusually, the front articulating surface of one of the caudal centra was undulating, being concave in the upper half and convex in the lower half. Poropat and colleagues suggested this as adistinguishing characteristic ofSavannasaurus. The other caudals wereamphicoelous, or having centra that are concave on both ends, which was also rare among titanosaurs save forBaotianmansaurus andDongyangosaurus.[3]
The only known cervical vertebra ofSavannasaurus is considered to have come from the rear of the neck due to its proportions. Unlike most titanosaurs but similar to the "ancestral" (plesiomorphic) condition among sauropods, the vertebra had a subtle keel running longitudinally along its bottom surface;Mendozasaurus,Overosaurus,Austroposeidon, andRapetosaurus also have such keels. There was a well-developed longitudinalfossa, or excavation, along the side of the vertebra that extends for nearly its entire length, unlike in many titanosaurs where it was faint or absent altogether. In contrast to more specialized titanosaurs like theSaltasauridae, theparapophysis (one of the rib articulations) was restricted to the front half of the centrum. Associated cervical rib fragments suggested that they were relatively long, extending for the length of at least three centra.[1][3]
Like many titanosaurs, the articulating surfaces of the dorsal centra inSavannasaurus were shorter vertically than they were wide. The dorsals have weakly-developed ridges bordering the sides of their bottom faces, as inDiamantinasaurus andOpisthocoelicaudia (where they were better developed), butSavannasaurus lacks the keel on the bottom of the centra as in these species. Like most other members of theSomphospondyli, the sides of the centra bore teardrop-shaped pneumatic holes. Thearticular processes at the front of the centra known as theprezygapophyses were connected by a sheet of bone (lamina), the transprezygapophyseal lamina; in the front dorsals, this sheet was V-shaped as in most titanosaurs, but it was basically flat in the rear dorsals unlike most other titanosaurs. Notably, the laminae in the dorsals ofSavannasaurus werebilaterally asymmetric; the left side of the vertebrae would have been better reinforced by extra laminae. Also unlikeOpisthocoelicaudia, the dorsalneural spines on top of the centra increased in height towards the rear dorsals, were not split into two, and were taller than their corresponding articular surfaces.[1][3]
In addition to the undulating articulating surface in one of the front caudal centra (caudal "A"), the two front caudals (caudals "A" and "B") ofSavannasaurus have another distinguishing characteristic. Like the non-titanosaur somphospondylanPadillasaurus, the front caudal centra had shallow pneumatic excavations on the sides surrounding small holes, whereas most members of the Somphospondyli have only the holes and not the excavations.[1] This characteristic had previously been regarded as a distinguishing characteristic of the non-somphospondylanbrachiosaurids.[5] Two other caudal vertebrae (caudals "C" and "D") are known from further back in the tail. The centra of caudals B, C, and D were about the same length, suggesting that centrum length did not vary considerably. However, both articulating surfaces were wider than tall in caudal C, while the front one was taller than wide in caudal D, suggesting that it was further forward than caudal D. Like other titanosauriforms, the processes that enclose theneural canal—the pedicles—in caudals C and D were two-thirds the length of the centra, and were shifted forwards relative to the midline.[3]
Two distinguishing characteristics ofSavannasaurus are found in the sternal plates. First, they were D-shaped with straight outer margins when viewed from the bottom, instead of being kidney-shaped as in other titanosaurs. Second, they lacked the long ridges that were present on the bottom surfaces among most members ofNeosauropoda. In general, the bottom surfaces were devoid of the grooves and pits on the top surfaces which are indicative of cartilage coverings. However, like most other titanosaurs, the sternal plates would have been at least 65% as long as the humeri (inSavannasaurus, the ratio was approximately 71%). The coracoid ofSavannasaurus was oval-shaped in side view, unlike the characteristically quadrangular coracoids of saltasaurids, and the glenoid fossa on it (which articulated with the humerus) was much larger than that ofDiamantinasaurus.[1] Unlike most titanosauriforms save forDaxiatitan,Ligabuesaurus, andSauroposeidon, the articulation with the scapula at the back of the bone was taller than the entire bone was long front to back.[3]
LikeDiamantinasaurus,Opisthocoelicaudia, and saltasaurids, the humerus ofSavannasaurus was robust. The radius was twisted about its axis, with the long axes of the two ends being oriented in different planes, seen otherwise only inHuabeisaurus,Epachthosaurus, andRapetosaurus. The maximum width of its top end (33% of the bone's length) and the presence of a strong ridge at the rear outer corner (the interosseous ridge) were more typical. Like all neosauropods, the hand digits ofSavannasaurus were arranged like a horseshoe. LikeDiamantinasaurus andWintonotitan, the third metacarpals were the longest, followed by the second, first, fourth, and fifth. The third metacarpal was 49% the length of the radius, which was short for a titanosaur, but was at least 45% as in all macronarians. A distinguishing feature is that the bottom of the fourth metacarpal was hourglass-shaped, not trapezoidal or hexagonal.[1] In life, the metacarpals would have been bound at the top and splayed at the bottom. The presence of phalanges is unusual; all titanosaurs butSavannasaurus andDiamantinasaurus had hands formed only by metacarpals. All digits but the first likely had phalanges, although their articulating surfaces on the bottoms of the metacarpals did not extend to the front as would be expected.[3]
The most distinctive feature ofSavannasaurus was the width of its pelvis[4]—its sacrum was 1.07 metres (3 ft 6 in) wide, and its fused ischium-pubis complex was at least 1.14 metres (3 ft 9 in) wide. Its sternal plates were around 85 centimetres (2 ft 9 in) wide to accommodate this. Although titanosaurs were wide-bodied in general, these proportions madeSavannasaurus extremely wide-hipped, surpassed only byOpisthocoelicaudia and saltasaurines such asNeuquensaurus.[1] Other pelvic proportions inSavannasaurus were also unusual. The ischium's articulation on the pubis was 56% as high as the bone was long, higher than most titanosaurs. The ischium inSavannasaurus was relatively short, being 63% as long as the pubis; it was at least 70% as long in all other titanosaurs butRapetosaurus (54%) andOpisthocoelicaudia (64%). A characteristic that distinguishedSavannasaurus from every other sauropod is that the front-to-back length of the ischium was only 42% of the bone's width. On the ischium, the iliac peduncle, one of the processes surrounding theacetabulum (hip joint), was only 32% of the bone's length, lower than most other sauropods. Furthermore, the front end of the ischium was 49% as wide as the bone was long; onlyDiamantinasaurus had a similarly high ratio (51%).[3]
Another distinguishing characteristic ofSavannasaurus is the presence of a subtle ridge that separates the front upper portion of the pubis from the rear plate. The ridge is parallel to another ridge just below the opening known as theobturator foramen; this latter ridge corresponds to multiple ridges inDiamantinasaurus. Also likeDiamantinasaurus, there was an expanded "boot" at the tip of the pubis. On the ischium, the ridge at the back which separated it from the pubis extended further to the side thanDiamantinasaurus, but less so thanWintonotitan. Further below, in the ankle, the height of the astragalus was greater than its diameters either front-to-back or side-to-side, which is unusual among titanosauriforms.[1] Two unusually low ratios in the astragalus are distinguishing features: the side-to-side diameter was 87% of the height, and the side-to-side diameter was 98% of the front-to-back diameter. UnlikeDiamantinasaurus, there was no shelf on the astragalus below where it would have articulated with thefibula.[3]
For their 2016 description, Poropat and colleagues conducted aphylogenetic analysis to test the affinities ofSavannasaurus and the new skull specimen ofDiamantinasaurus. They added these specimens to a dataset created by Philip Mannion (one of the co-authors of the description ofSavannasaurus) and colleagues for the 2013 redescription ofLusotitan.[6] The analysis placedSavannasaurus andDiamantinasaurus together in aclade (unified group) close to the root of Titanosauria, outside thederived (specialized) groupLithostrotia.[1] Similar results were recovered by Rafael Royo-Torres and colleagues in their 2017 description ofSoriatitan;[7] Mannion and colleagues in their 2017 description ofVouivria;[8] Alexander Averianov and Vladimir Efimov in their 2018 description ofVolgatitan;[9] Bernardo Gonzàlez Riga and colleagues in their 2018 redescription ofMendozasaurus;[10] and Pedro Mocho and colleagues in their 2019 descriptions of an indeterminate lithostrotian[11] andOceanotitan.[12]
In 2020, Poropat and colleagues noted a number of features that support a position forSavannasaurus outside Lithostrotia: the horizontal transprezygapophyseal laminae, the lack of constriction in the vertebrae of the sacrum, the amphicoelous caudal centra, the pneumatic excavations on the front caudals, the D-shaped sternal plates, the presence of phalanges, and the lack of a longitudinal ridge on the side of the pubis. At the same time, the lack of hyposphene-hypantrum articulations in the dorsal and caudal vertebrae provides evidence against a morebasal (non-specialized or rootward) position, given their presence in many non-titanosaur titanosauriforms and rarity among titanosaurs.[6] Some titanosaurs also had these articulations; the basalAndesaurus and the lithostrotianEpachthosaurus had them in the dorsals, while the lithostrotiansEpachthosaurus,Opisthocoelicaudia,Volgatitan, andMalawisaurus had them in the caudals. However, Poropat and colleagues recognized the possibility that they could have been acquired independently multiple times among titanosaurs.[3]
Nevertheless, other phylogenetic analyses based on Mannion and colleagues' 2013 dataset have found different results. Royo-Torres and colleagues repeated their 2017 analysis after removing a titanosauriform from theCloverly Formation,Chubutisaurus, andAngolatitan; they found instead thatSavannasaurus andDiamantinasaurus were successively basal to a clade consisting ofBaotianmansaurus andDongyanosaurus.[7]Savannasaurus shared amphicoelous caudal centra with both genera, various features of vertebral laminae withBaotianmansaurus, and unkeeled dorsal centra and the absent longitudinal ridge on the side of the pubis withDongyanosaurus. However, unlikeSavannasaurus,Baotianmansaurus had hyposphene-hypantrum articulations, and both genera had bifid dorsal neural spines (i.e., split into two).[3]
Similarly, for a 2019 paper naming the new cladeColossosauria, Gonzàlez Riga and colleagues extended their 2018 phylogenetic analysis and found an unresolvedpolytomy ofSavannasaurus,Baotianmansaurus,Dongyanosaurus, and a clade of more derived titanosaurs.Diamantinasaurus was placed in a more derived position as thesister group of Lithostrotia.[13] Also in 2019, Julian Silva Jr. and colleagues extended the 2018 analysis of Gonzàlez Riga and colleagues for their redescription ofUberabatitan. They foundSavannasaurus outside the Titanosauria in a polytomy withEuhelopus,Erketu,Qiaowanlong, a clade ofTangvayosaurus andPhuwiangosaurus, and more derived somphospondyls; they also foundDiamantinasaurus andBaotianmansaurus to form a clade inside the Saltasauridae.[14] Poropat and colleagues considered their results unusual in 2020.[3] In their 2019 redescription ofJiangshanosaurus andDongyanosaurus, Mannion and colleagues found bothSavannasaurus andDiamantinasaurus inside Saltasauridae by equally weighting characteristics in their dataset, but usingimplied weighting eliminated this result.[15]
The phylogenetic tree from the analysis of Poropat and colleagues in 2016 is reproduced below, at left, with emphasis on relevant clades.[1] An alternative tree by Royo-Torres and colleagues in 2017, from the analysis that removed the Cloverly titanosauriform,Chubutisaurus, andAngolatitan, is also shown at right.[7]
Topology A: Poropatet al. (2016)[1]
Topology B: Royo-Torreset al. (2017)[7]
| Titanosauriformes |
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As the southernsupercontinent ofGondwana broke up during theCretaceous period, dinosaur faunas became more diverse.[16] Conventional hypotheses suggest that the faunas from the Gondwanan continents (including Australia) would be closely related,[17] but mid-Cretaceous Australian dinosaurs have been found to be more closely related to theirLaurasian (northern) counterparts in spite of the fact that Laurasia and Gondwana had already been separated by theTethys Ocean for a significant span of time.[18][19] In 2016, Poropat and colleagues tested this hypothesis by performing apalaeobiogeographic analysis using the results of their phylogenetic analysis. Using the modern geography of the continents, they found that the ancestors of the Australian sauropodsSavannasaurus,Diamantinasaurus, andWintonotitan were likely Asian. Incorporating Cretaceous geography suggested ancestral ranges also spanning the Gondwanan continents of South America, Africa, and Indo-Madagascar.[1]
Combining their palaeobiogeographic analysis with time-calibrated phylogenies based on fossil age estimates, Poropat and colleagues inferred that somphospondylans and titanosaurs had attained a wide distribution across the world by theBarremian epoch, 131 to 125 million years ago, if not earlier. However, they ultimately diverged into a number of lineages ultimately with limited geographical ranges; they attributed this endemism toregional extinction events. They estimated that theSavannasaurus+Diamantinasaurus andWintonotitan lineages had separately reached Australia no later than the lateAlbian epoch, 105 to 100 million years ago, but the exact timing depended on the models that they used. The oldest Australian titanosauriforms,Austrosaurus and the "Hughenden sauropod", date to this interval.[1][20]
Although they acknowledged the possibility ofsampling biases, Poropat and colleagues considered a late Albian dispersal likely because of the most probable dispersal route, which would have entailed beginning from South America and crossing through Antarctica to southeastern Australia. In theAptian to early Albian epochs, this region of Australia would have been situated at alatitude of 70°S, with a cool, temperate climate.[21] No sauropods have been found from these latitudes and environments, suggesting that they were adapted to warm climates and avoided these regions. Thus, they would likely have been unable to disperse across Antarctica until the late Albian, whenglobal warming led to a smoother temperature gradient.[22][23] Poropat and colleagues suggested that climate preferences could also explain the Laurasian affinities of Australian dinosaurs.[1]
In 2020, Tai Kubo appliednetwork analysis to a phylogenetic "supertree" of Australian dinosaurs. He found a strong connection between Australian dinosaur faunas and other Gondwanan dinosaurs, and identified Gondwanan Cretaceous dinosaurs as a distinct community. Thus, he suggested that most previous results identifying affinities between Australian and Laurasian dinosaurs were caused by insufficient sampling of Gondwanan dinosaurs and the phylogenetic instability of Australian dinosaurs. For instance, he pointed out that themegaraptoranAustralovenator was thought to be an offshoot of an Asian lineage until more Gondwanan megaraptorans were found. While he suggested that the same was true of these sauropods, he also recognized the possibility that they had a different biogeographical history than smaller dinosaurs.[24]
Like all titanosaurs,Savannasaurus was likely a "wide-gauge" sauropod, meaning that it would have stood and walked with its feet far apart from the midline.[25] In 2020, Poropat and colleagues pointed to the width of its sternal plates and sacrum as evidence for a wide-gauge stance. The robust humerus ofSavannasaurus was also considered a likely adaptation to a wide-gauge stance, which would have beenconvergently acquired with saltasaurines. They also suggested that the unusual form of the astragalus was also an adaptation to weight-bearing, but the absence of other hindlimb bones made this unclear. Yet, Poropat and colleagues also noted traits that would have increased the flexibility of the vertebral column, namely the absence of hyposphene-hypantrum articulations and the presence of prominent excavations (the centroprezygapophyseal fossae) below the transprezygapophyseal laminae. Both of these were shared withDiamantinasaurus, but were otherwise rare among sauropods.[1][3]
Poropat and colleagues noted that bothSavannasaurus andDiamantinasaurus would have lived on afloodplain withclay-rich soil and high rainfall (see§ Palaeoecology), which would imply that the ground would occasionally become muddy and hazardous for large sauropods. They considered it possible that environmental pressures would haveselected for individuals capable of navigating muddy ground, and thatSavannasaurus might have spent more time near water than other sauropods. Flexible vertebrae (to escapebogs), barrel-like bodies similar to those ofhippopotami, wide-gauge stance, and robust forelimbs (all to distribute its body weight) would all have been helpful for such aniche. They postulated that saltasaurines might have been subject to similar selective pressures, and so the "typical" titanosaur bodyplan may have been acquired convergently multiple times. While the same environment could also have selected for longer necks to provide easier access to water, Poropat and colleagues noted thatSavannasaurus andDiamantinasaurus likely had relatively short necks, though overlapping cervical ribs might have improved stability inSavannasaurus.[3]
The Belmont sheep station is part of the fossil-bearing rock units in the upperWinton Formation, which has been dated to around or just after theboundary between theCenomanian andTuronian epochs of the Cretaceous—about 93.9 million years ago—based onuranium-lead dating of detritalzircons.[26] It is the geologically youngest rock unit of theMesozoic era in theEromanga Basin. Six majorfacies, or distinct rock types, are found in the Winton Formation: two different types ofsandstone-siltstone combinations (associated with meandering rivers,crevasse splays, andlevees),mudstones (associated withoxbow lakes and ponds), sandy siltstones to silty mudstones (associated withtidal flats), plant-rich mudstone andcoal (associated with swampy ground),intraformational conglomerates (associated with flooding). These rocks suggest thatSavannasaurus lived on a freshwater floodplain covered in broad,meandering river channels with low-energy waterflow, which was subject to occasional flooding.[27][28]
During the Cenomanian and Turonian, the Winton area had a latitude of around 50°S. Leaf fossils show that the climate was warm, with a mean annual temperature of 16 °C (61 °F), and wet, with a mean annual precipitation of over 1,300 millimetres (51 in). Although the weather was seasonal, there was no extreme cycle between thewet season anddry season as is the case today. Thegrowing season would have been eight to nine months long. However, weather patterns also appeared to have been cyclical on a multi-year basis, similar to the modernPacific decadal oscillation; this may also have influenced the sporadic flooding.Conifers andangiosperms were the most common plants in the Winton Formation; conifers included thecypressAustrosequoia, thearaucariasAraucaria andEmwadea, and thepodocarpProtophyllocladoxylon, while angiosperms includedLovellea and various unnamed forms. Other plants included thefernsPhyllopteroides andTempskya; theliverwortMarchantites; thehorsetailEquisetites; thebennettitaleansOtozamites andPtilophyllum; and theginkgoaleanGinkgo.[3][28]
Savannasaurus lived alongside a diverse vertebrate fauna in the upper Winton Formation.[26] Contemporary dinosaurs included the sauropodsDiamantinasaurus matildae andWintonotitan wattsi, the megaraptoran theropodAustralovenator wintonensis, and indeterminateankylosaurians andhypsilophodonts. A tooth belonging toAustralovenator was found near theSavannasaurus holotype, suggesting that its feeding was responsible for the specimen's disarticulation. Otherarchosaurs included thepterosaurFerrodraco lentoniT[29] and thecrocodilianIsisfordia duncani, along with other undescribed pterosaurs and crocodilians. Additional vertebrates known from the Winton Formation arechelid turtles; an indeterminatevaranoid lizard;[30] thelungfishMetaceratodus ellioti andM. wollastoni; andray-finned fish includingCladocyclus geddesi.[31] Invertebrates were dominated by thebivalvesAlathyria jaqueti,Hyridella goondiwindiensis,Megalovirgus wintonensis, andProhyria macmichaeli, but also included thegastropodMelanoides,dragonflies,scorpionflies, andoribatid mites known fromtrace fossils found insilicified wood.[3][28][32]
