Tyrannomimus fukuiensis: A new Ornithomimosaur from the Early Cretaceous of Japan, and its implications for the origins of the Ornithomimosauria.

The Ornithomimosaurs are a group of Theropod Dinosaurs with notably long and slender hindlimbs, thought to have been capable of sustained high-speed running in a similar fashion to modern Ostriches. This Ostrich-like appearance is accentuated by their having feathers, long necks, small heads, and often-toothless beak-like jaws. The earliest known Ornithomimosaurs date from the Early Cretaceous, with the two major subdivisions of the group, the Ornithomimidae and Deinocheiridae apparently having already diverged by this time, implying a deeper 'ghost' history to the clade, which has not been detected in the fossil record.

In a paper published in the journal Scientific Reports on 7 September 2023, Soki Hattori, Masateru Shibata, Soichiro Kawabe, Takuya Imai,  Hiroshi Nishi, and Yoichi Azuma of the Institute of Dinosaur Research at Fukui Prefectural University, and the Fukui Prefectural Dinosaur Museum, describe a new species of Ornithomimosaur from the Early Cretaceous Kitadani Formation exposure at Kitadani Dinosaur Quarry.

Kitadani Dinosaur Quarry is a notable Dinosaur-producing site in Fukui Prefecture, which has previously produced a number of new Dinosaur species, including the Therizinosaur, Fukuivenator paradoxus, which is the most complete non-Avian Dinosaur known from Japan, the Titanosaur, Fukuititan nipponensis, the Megaraptor, Fukuiraptor kitadaniensis, and the Iguanodontian, Fukuisaurus tetoriensis.

Bonebed 1 is a distinct layer within the Kitadani Formation at Kitadani Dinosaur Quarry containing a large number of disassociated Dinosaur bones interpretted as having come from a single species of Ornithomimosaur, which Hattori et al. formally describe as a new species, under the name Tyrannomimus fukuiensis, where 'Tyrannomimus' refers to the similarity of the species to some (small) Tyrannosaurs, in particular its possession of a vertical ridge on the ilium, a feature previously interpreted as a defining Tyrannosaur trait, and 'fukuiensis' means 'from Fukui'.

Locality, horizon, and overview of the Ornithomimosaur materials. Regional map for the location of Fukui in Japan, and the Kitadani Dinosaur Quarry in Fukui (a), stratigraphic section of the part of the Kitadani Formation in the Kitadani Dinosaur Quarry (b), photograph of the Kitadani Dinosaur Quarry in 2019 with an arrowhead indicating where the studied specimens were discovered (c), and overview of the Ornithomimosaur material (d). Fossil specimens shown in (d) are not in the same scale while the bar is scaled for the paratype (FPDM-V-10295). The holotype (FPDM-V-11333) and paratype in (d) are colored in red anb blue, respectively. Right femur in (d) is mirrored from a left femur (FPDM-V-11338). Hatorri et al. (2023).

Tyrannomimus fukuiensis is described from a holotype, FPDM-V-11311, a disarticulated but associated skeleton including two parts of the braincase, several dorsal, sacral and caudal vertebrae, and fragments of ilium, and paratype, FPDM-V-10295, a disarticulated but associated hindlimb skeleton including a partial lef femur, left metatarsal II, lef and right metatarsal IV, right pedal phalanx I-1 and a pedal ungual, with reference to several other specimens.

Cranial elements of Tyrannomimus fukuiensis. Left frontal of FPDM-V-11313 (a)–(c) and right prootic (mirrored) (d)–(f), osseous labyrinth (mirrored) (g)–(i) and basioccipital (j)–(l) of FPDM-V-11311 in dorsal (a), (g), lateral (b), (f), (i), (j), ventral (c), (l), dorsolateral (d), anterior (e), (h) and posterior (k) views. Abbreviations: br, basisphenoid recess; bt, basal tuber; cd, cochlear duct; dtr, dorsal tympanic recess; if, infracondylar fossa; lc, lacrimal contact; ls, lateral semicircular canal; lsc, laterosphenoid contact; om, orbital margin; or, orbitonasal ridge; pfc, prefrontal contact; poc, postorbital contact; pop, postorbital process; rs, rostral semicircular canal; sf, supratemporal fossa; sr, subcondylar recess; V, trigeminal nerve opening; VII, facial nerve opening. Scale bars are equal to 10 mm. Hatorri et al. (2023).

Bonebed 1 contains a very large number of detached bones, but this appears to be a monospecific assemblage, with little variation among any of the individual skeletal elements. The holotype of Tyrannomimus fukuiensis does not appear to be fully mature, which might raise the possibility that it is a juvenile of another species, notably Fukuiraptor kitadaniensis, which is also present at Kitadani Dinosaur Quarry and of nearly identical age. However, the holotype of Tyrannomimus does not show any of the diagnositic features of Fukuiraptor, while it shows a number of diagnostic features of the Ornithomimosaurs and is clearly monospecific with the other material from Bonebed 1, effectively ruling out such a hypothesis.

A phylogenetic analysis recovered Tyrannomimus fukuiensis as a member of the Deinocheiridae, forming a sister taxon to the Mongolian Harpymimus okladnikovi. This analysis also makes Tyrannomimus fukuiensis the oldest known member of the Deinocheiridae, and the first member of that group from East Asia. This close relationship between the Japanese Tyrannomimus fukuiensis and the Mongolian Harpymimus okladnikovi is noteworthy, as other Early Cretaceous Japanese fossils, including Hadrosaurs and Cockroaches have also shown closer affinity to Mongolian groups than to Chinese ones, suggesting an ecological link between the two areas.

Phylogenetic position of Tyrannomimus fukuiensis within Ornithomimosauria. A coloured bar in the strict consensus tree represents the time and region of occurrence for each taxon and a number represents Bremer support value for each node. Note that the dataset for the phylogenetic analysis that yielded this consensus tree did not include Aviatyrannis. Hatorri et al. (2023).

The presence of a vertical ridge on the ilium of Tyrannomimus fukuiensis makes it very similar to the ilium of Aviatyrannis jurassica, a Theropod Dinosaur from the Late Cretaceous of Portugal, currently assumed to be a Tyrannosaurid, largely due to the possession of this feature. Aviatyrannis jurassica has a number of other features, such as a brevis fossa which becomes mediolaterally broader towards the posterior end, which are typical of Ornithomimosaurs. A phylogenetic analysis of the Ornithomimosauria with Aviatyrannis jurassica included recovered this Jurassic 'Tyrannosaur' as the sister taxon to Tyrannomimus fukuiensis. If this is correct then Aviatyrannis jurassica is in fact both the earliest known Ornithomimosaur and the earliest known Deinocheirid, although without having inspected the holotype of Aviatyrannis jurassica themselves, Hatorri et al. are cautious in this assessment.

Strict consensus tree of 2640 MPTs with a length of 3019 steps (CI = 0.217; RI = 0.608) resulted by the phylogenetic analysis conducted with Aviatyrannis jurassica being added. Numbers associated with nodes represent Bremer support values. Hatorri et al. (2023).

The oldest known specimens currently recognised as Ornithomimosaurs are un-named fragmentary specimens from the Kirkwood Formation of South Africa, followed by fragmentary specimens assigned to Valdoraptor oweni, un-named fragmentary specimens from France, and some fragmentary material from Thailand described as Kinnareemimus khonkaenensis. A putative Ornithomimosaur, Lepidocheirosaurus natatilis, has previously been described from the Late Jurassic  Kulinda Deposits of Zabaykalsky Krai, Russia, but it is now considered doubtful that this is even a Theropod. If Lepidocheirosaurus natatilis is not an Ornithomimosaur, and Aviatyrannis jurassica is, then Aviatyrannis jurassica would be the oldest known and only Jurassic member of the Ornithomimosauria. This is not implausible, as the Ornithomimosauria are considered to be the sister taxon to the Maniraptora, a group which appeared in the Middle Jurassic, making it unlikely that the Ornithomimosauria are significantly younger. Furthermore, the distribution of the earliest known Ornithomimosaurs suggests that the group appeared before the break-up of Pangea, making a Cretaceous origin improbable. 

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Fukuivenator paradoxus: A Maniraptoran Theropod from the Early Cretaceous of

The Maniraptorans were a highly diverse and successful group of Theropod Dinosaurs, whose members included the Dromaeosaurs, Troodontids and Birds. For a long while this group was overlooked in favour of more massive Theropod groups, however in recent years this group has been extensively studied, with numerous specimens discovered on several continents, leading to a better understanding of the group's evolution and diversity. Japan has relatively little exposed Tertiary terrestrial sediment, and subsequently has produced few Dinosaur specimens, and less of any great quality. One site known to produce high quality terrestrial fossils in Japan is the Kitadani Dinosaur Quarry in Fukui Prefecture, which has produced numerous Dinosaur remains, as well as Pterosaurs, Crocodyliforms, Turtles, Mammals, Invertebrates and Plants.

In a paper published in the journal Nature Scientific Reports on 23 February 2016, a team of scientist led by Yoichi Azuma of the Institute of Dinosaur Research at Fukui Prefectural University and the Fukui Prefectural Dinosaur Museum describe a new Maniraptoran Dinosaur from the Kitadani Dinosaur Quarry, which is clearly a Maniraptoran, but which does not appear to belong to any known Maniraptoran group.

The new Dinosaur is named Fukuivenator paradoxus, where 'Fukuivenator' means 'Fukui-hunter' and 'paradoxus' refers to the surprising combination of features seen in the specimen. Fukuivenator paradoxus is in many ways similar to a Dromaeosaur, but has a number of feature more typical of other Maniraptoran groups, such as a premaxilla (bone at the tip of the upper jaw) with a broad subnarial shelf and a long maxillary process extending backwards, a feature typical of Ornithomimosaurs, enlarged promaxillary fenestra (paired holes above the jaw in Dinosaurs and other Diapsids), a feature seen in early Troodontids and Birds, a lacrimal bone (bone on the inner side of each eye socket) with a T-shape in profile, another feature associated with Troodontids and at least 11 cervical (neck) vertebrae, a feature otherwise known only in Birds. 

Cranial skeletal morphology of Fukuivenator paradoxus. (a) Partial right premaxilla in lateral view. (b) Partial left maxilla in lateral view. (c) Partial left lacrimal in lateral view. (d) Right frontal in dorsal view. (e) Right postorbital in lateral view. (f) Left squamosal in lateral view. (g) Partial right dentary in lateral view. Scale bar is 10 mm. Abbreviations: aofe, antorbital fenestra; en, external naris; mxfe; maxillary fenestra, prfe; premaxillary fenestra. Azuma et al. (2016).

Fukuivenator paradoxus also shows a number of features not seen in any other Maniraptoran Dinosaur, most notably heterodont dentition (different teeth in different parts of the jaw), a feature extremely rare in Dinosaurs and not previously recorded in any Theropod, and unserrated teeth, oval in profile, unlike the serrated blade-shaped teeth of most Theropods. 

Premaxillary and maxillary teeth of Fukuivenator paradoxus. (a) Isolated anteriormost? premaxillary tooth in lateral (left) and posterior (right) views. (b) Enlarged view of the crown in (a) lateral (left), anterior (middle), and posterior (right) views. (c) Crown of an isolated left premaxillary tooth in distal (left), lateral (middle), mesial (right) views with an enlarged view of the mesial “ridge” (red box). (d) Intact left maxillary teeth in lateral view. Scale bar is 10 mm for (a,d), 7.5 mm for (b), and 12.5 mm for (c). Azuma et al. (2016).

Azuma et al. suggest that the unusual dentition and long neck of Fukuivenator paradoxus may hold the key to its unusual morphology, and note that other in other Theropod groups the development of unique dentition has been conected to elongation of the neck, and suggests that these features combined probably indicate a move away from a strictly carnivorous diet.

See also...

Boreonykus certekorum: A new species of Velociraptorine Dromaeosaur from the Late Cretaceous of west-cemtral Alberta.   Dromaeosaurs are thought to have been the group of Theropod Dinosaurs most closely related to birds, making them of great interest to palaeontologists. They were smal-to-medium sized predatory Dinosaurs, which all appear to have had extensive featheres plumage...

Partial Dromaeosaur remains from the Early Cretaceous of Inner Mongolia.          Dromaeosaurs are thought to have been the Dinosaur group most closely related to the earliest Birds, making them of great interest to palaeontologists...

Dakotaraptor steini: A giant, feathered Dromaeosaurid from the End Cretaceous Hell Creek Formation of South Dakota. Dromaeosaurids were first described in the 1920s, but received relatively little attention from palaeontologists until the late 1960s. However in recent years it has been realized that the group were...

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One person confirmed dead and two more missing as Typhoon Man-yi hits Japan.

A 71 year old woman has been confirmed dead after a landslip hit her home in Ritto City in Shiga Prefecture, Japan, on Monday 16 September 2013 following heavy rains associated with Typhoon Man-yi. Landslides are a common problem after severe weather events, as excess pore water pressure can overcome cohesion in soil and sediments, allowing them to flow like liquids. Approximately 90% of all landslides are caused by heavy rainfall. Two more people are missing in Fukui and Hyogo Prefectures, where there has been extensive flooding, and around 200 000 people have been evacuated from their homes across the Kansai Region of south-central Honshū.

Flooding along the River Katsura in Kyoto, Japan, following the arrival of Typhoon Man-yi in the area. Kyodo News/AP.

Tropical storms are caused by solar energy heating the air above the oceans, which causes the air to rise leading to an inrush of air. If this happens over a large enough area the inrushing air will start to circulate, as the rotation of the Earth causes the winds closer to the equator to move eastwards compared to those further away (the Coriolis Effect). This leads to tropical storms rotating clockwise in the southern hemisphere and anticlockwise in the northern hemisphere.These storms tend to grow in strength as they move across the ocean and lose it as they pass over land (this is not completely true: many tropical storms peter out without reaching land due to wider atmospheric patterns), since the land tends to absorb solar energy while the sea reflects it.

The low pressure above tropical storms causes water to rise there by ~1 cm for every millibar drop in pressure, leading to a storm surge that can overwhelm low-lying coastal areas, while at the same time the heat leads to high levels of evaporation from the sea - and subsequently high levels of rainfall. This can cause additional flooding on land, as well as landslides.

See also Three dead as Tropical Storm Kong-Rey batters Taiwan, Widespread flooding as Typhoon Trami hits Fujian Province, China, Typhoon Utor hits south China, At least one person dead as Typhoon Utor sweeps across Luzon Island and Four confirmed dead in landslide in Akita Prefecture, Japan.

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