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41-564: Parankylosauria is a group of basal ankylosaurian dinosaurs known from the Cretaceous of South America , Antarctica , and Australia . It is thought the group split from other ankylosaurs during the mid- Jurassic period, despite this being unpreserved in the fossil record. During the Mesozoic era, the southern continents ( South America , Antarctica , Australia , and Africa in addition to India and Zealandia ) were unified into

82-493: A biogeographic connection between South America and ankylosaurs in Australia was raised alongside discovery, though based on conjecture. Ankylosaurs from Gondwana have remained very mysterious. Fossil material continues to be scant and southern taxa have been difficult to interpret in a phylogenetic context. Vertebrae of Antarctopelta from Antarctica, for example, were so foreign compared to those of euankylosaurs that it

123-616: A supercontinent known as Gondwana . This was in contrast to the supercontinent of Laurasia in the Northern Hemisphere , with both originating from the breakup of Pangaea . Gondwana itself gradually split apart over the course of the Jurassic and Cretaceous eras. Ankylosaurian dinosaurs from Laurasia have historically been far more extensively recorded and studied. Reports of the group in Gondwana date back to 1904, with

164-409: A correlation does not make a given case predicable, so ancestral characters should not be imputed to the members of a less species-rich basal clade without additional evidence. In general, clade A is more basal than clade B if B is a subgroup of the sister group of A or of A itself. In the context of large groups, the term "basal" is often used loosely to refer to positions closer to

205-470: A formal definition for Thyreophoroidea in the PhyloCode as "the smallest clade containing Ankylosaurus magniventris , Scelidosaurus harrisonii , and Stegosaurus stenops ". The following cladogram shows the results of the phylogenetic analysis Soto-Acuña et al . (2021). In their description of Jakapil the following year, Riguetti et al modified the same matrix and found it to occupy

246-698: A mix of archaic and apomorphic (derived) features that have only been sorted out via comparison with other angiosperms and their positions within the phylogenetic tree (the fossil record could potentially also be helpful in this respect, but is absent in this case). The cladogram below is based on Ramírez-Barahona et al. (2020), with species counts taken from the source indicated. Amborellales (1 species) Nymphaeales (about 90 species) Austrobaileyales (about 95 species) Magnoliids (about 9,000 species) Chloranthales (about 80 species) Monocots (about 70,000 species) Ceratophyllales (about 6 species) Eudicots (about 175,000 species) Within

287-402: A new specimen (SAMA P40536) tentatively referred to Kunbarrasaurus tested their new specimen in the dataset of the 2021 study, finding a similar placement and composition of Parankylosauria, but also coded the specimen for an older phylogenetic dataset of a 2016 paper by Victoria Arbour and Phil Currie . The resulting analysis found Kunbarrasaurus and the new specimen to nest together in

328-470: A position as the sister taxon to the Eurypoda. A similar result was found by Fonseca et al. in 2024. Laquintasaura Lesothosaurus Emausaurus Scelidosaurus [REDACTED] Yuxisaurus Jakapil Euankylosauria [REDACTED] In 2020, as part of his monograph on Scelidosaurus , David Norman revised the relationships of early thyreophorans, finding that Stegosauria

369-428: A similar position on the tree to where Parankylosauria was found in the 2021 dataset, supporting that conclusion. The tree of the second dataset is reproduced below: Lesothosaurus Scelidosaurus Huayangosaurus Kunbarrasaurus SAMA P40536 Mymoorapelta Nodosauridae Ankylosauridae Basal (phylogenetics) While there must always be two or more equally "basal" clades sprouting from

410-473: A sister group to Homininae and are the basal genus in the great ape family Hominidae as a whole. Orangutans ( Pongo spp.) Humans ( Homo sapiens ) Chimpanzees ( Pan spp.) Gorillas ( Gorilla spp.) Subfamilies Homininae and Ponginae are both basal within Hominidae, but given that there are no nonbasal subfamilies in the cladogram it is unlikely the term would be applied to either. In general,

451-461: A specimen from Australia and include referrals of Loricosaurus , Lametasaurus , and Brachypodosaurus to group among assorted fragmentary material. Much of this material including would later be shown to be misidentified and not belonging to ankylosaurs, including the named genera. The first definitive ankylosaur to be recognized from Gondwana was discovered in Australia in 1964 and later named in 1980 as Minmi paravertebra . The possibility of

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492-405: A statement to the effect that one group (e.g., orangutans) is basal, or branches off first, within another group (e.g., Hominidae) may not make sense unless the appropriate taxonomic level(s) (genus, in this case) is specified. If that level cannot be specified (i.e., if the clade in question is unranked) a more detailed description of the relevant sister groups may be needed. As can be seen, the term

533-461: A trait generally viewed as ancestral among the apes. Given that the deepest phylogenetic split in a group is likely to have occurred early in its history, identification of the most basal subclade(s) in a widely dispersed taxon or clade can provide valuable insight into its region of origin; however, the lack of additional species in a clade is not evidence that it carries the ancestral state for most traits. Most deceptively, people often believe that

574-553: Is a basal clade of extant angiosperms , consisting of the most species, genus, family and order within the group that are sister to all other angiosperms (out of a total of about 250,000 angiosperm species). The traits of Amborella trichopoda are regarded as providing significant insight into the evolution of flowering plants; for example, it has "the most primitive wood (consisting only of tracheids ), of any living angiosperm" as well as "simple, separate flower parts of indefinite numbers, and unsealed carpels". However, those traits are

615-638: Is a group of armored ornithischian dinosaurs that lived from the Early Jurassic until the end of the Cretaceous . Thyreophorans are characterized by the presence of body armor lined up in longitudinal rows along the body. Primitive forms had simple, low, keeled scutes or osteoderms , whereas more derived forms developed more elaborate structures including spikes and plates. Most thyreophorans were herbivorous and had relatively small brains for their body size. Thyreophora includes two major subgroups, Ankylosauria and Stegosauria . In both clades,

656-458: Is defined as the largest clade containing Ankylosaurus magniventris and Stegosaurus stenops but not Iguanodon bernissartensis and Triceratops horridus . They also defined the less inclusive Eurypoda as "the smallest clade containing Ankylosaurus magniventris and Stegosaurus stenops " to include the ankylosaurs and stegosaurs to the exclusion of basal thyreophorans. A later study conducted by André Fonseca and colleagues in 2024 gave

697-415: Is likely a source of the mis-use of the term. Other famous examples of this phenomenon are the oviparous reproduction and nipple-less lactation of monotremes , a clade of mammals with just five species, and the archaic anatomy of the tuatara , a basal clade of lepidosaurian with a single species. The flowering plant family Amborellaceae , restricted to New Caledonia in the southwestern Pacific,

738-515: Is not reflective of ancestral states or proximity to the common ancestor of extant species. In this example, orangutans differ from the other genera in their Asian range. This fact plus their basal status provides a hint that the most recent common ancestor of extant great apes may have been Eurasian (see below), a suggestion that is consistent with other evidence. (Of course, lesser apes are entirely Asiatic.) However, orangutans also differ from African apes in their more highly arboreal lifestyle,

779-432: Is reproduced from the phylogenetic analysis in the 2021 study by Sergio Soto-Acuña and colleagues: Lesothosaurus Scutellosaurus Emausaurus Scelidosaurus Huayangosaurus Stegosauridae Kunbarrasaurus Antarctopelta Stegouros Nodosauridae Liaoningosaurus Gobisaurus Shamosaurus Ankylosaurinae In 2022, a study by Timothy G. Frauenfelder and colleagues on

820-418: Is unnecessary and misleading. The term is more often applied when one branch (the one deemed "basal") is less diverse than another branch (this being the situation in which one would expect to find a basal taxon of lower minimum rank). The term may be equivocal in that it also refers to the direction of the root of the tree, which represents a hypothetical ancestor; this consequently may inaccurately imply that

861-590: The great apes , gorillas (eastern and western) are a sister group to chimpanzees , bonobos and humans . These five species form a clade, the subfamily Homininae (African apes), of which Gorilla has been termed the basal genus. However, if the analysis is not restricted to genera, the Homo plus Pan clade is also basal. Humans ( Homo sapiens ) Bonobos ( Pan paniscus ) Chimpanzees ( Pan troglodytes ) Eastern gorillas ( Gorilla beringei ) Western gorillas ( Gorilla gorilla ) Moreover, orangutans are

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902-411: The acquisition of advanced skull traits earlier in ankylosaur evolution. Also unlike euankylosaurs, it is thought, based on the preserved osteoderms of Kunbarrasaurus and lack of flank osteoderms associated with other known genera, that parankylosaurs may not have had rather light coverings of dermal armor compared to their relatives. They possessed a pelvic shield, formed from a thin sheet of bone over

943-399: The body of parankylosaurs, functioning as spiny armor. Parankylosaurs, compared to the more well studied euankylosaurs, retain more traits seen in more primitive thyreophorans and stegosaurs. This is most applicable in the body, most distinctively seen in the possession of rather long and slender limbs. The skull, comparatively, is more similar to that of other ankylosaurs, thought to indicate

984-521: The direction of migration away from the area of origin can also be inferred (as in the Amaurobioides and Noctilionoidea cases below). As with all other traits, the phylogeographic location of one clade that connects to the root does not provide information about the ancestral state. Examples where such unjustified inferences may have been made include: Thyreophora Thyreophora ("shield bearers", often known simply as "armored dinosaurs")

1025-582: The entirety of it near the tip. This weapon is known directly in the genus Stegouros , suspected based on indirect evidence in Antarctopelta , and not confirmed in Kunbarrasaurus , for which a complete tail is not known. In the former taxon the weapon is associated with dramatic shortening of the tail, made up of far fewer vertebrae than any other kind of thyreophoran . As with many other members of this group, osteoderms would have covered much of

1066-719: The extant taxa of a given rank within the clade; this is one reason the term basal is highly deceptive, as the lack of additional species in one clade is taken as evidence of morphological affinity with ancestral taxa. Additionally, this qualification does not ensure that the diversity of extinct taxa (which may be poorly known) is represented. In phylogenetics, the term basal cannot be objectively applied to clades of organisms, but tends to be applied selectively and more controversially to groups or lineages thought to possess ancestral characters, or to such presumed ancestral traits themselves. In describing characters, "ancestral" or " plesiomorphic " are preferred to "basal" or " primitive ",

1107-403: The following case:   Basal clade #1  Non-basal clade #1  Non-basal clade #2    Non-basal clade #3 While it is easy to identify a basal clade in such a cladogram, the appropriateness of such an identification is dependent on the accuracy and completeness of the diagram. It is often assumed in this example that the terminal branches of the cladogram depict all

1148-466: The forelimbs were much shorter than the hindlimbs, particularly in stegosaurs. Thyreophora has been defined as the group consisting of all species more closely related to Ankylosaurus and Stegosaurus than to Iguanodon and Triceratops . It is the sister group of Cerapoda within Genasauria . Members of Thyreophora are characterised by the presence of osteoderms (bony growths within

1189-412: The group is their macuahuitl, named after the mesoamerican weapon of the same name. This trait is similar to the thagomizer of stegosaurs and tail clubs known in ankylosaurines , though evolved independently from each. This was a structure at the end of the tail formed by a series of five pairs of robust osteoderms (bones in the skin) fused together, surrounding the sides of the tail and surrounding

1230-468: The hip region, more reinforced than the superficial shielding of stegosaurs but not as overbuilt as those found in euankylosaurs. André Fonseca and colleagues in 2024 formally defined this clade in the PhyloCode as "the largest clade containing Stegouros elengassen , but not Ankylosaurus magniventris and Nodosaurus textilis ". This definition ensures both ankylosaurids and nodosaurids are excluded from Parankylosauria. The following cladogram

1271-437: The latter of which may carry false connotations of inferiority or a lack of complexity. The terms ''deep-branching'' or ''early-branching'' are similar in meaning, and equally may misrepresent extant taxa that lie on branches connecting directly to the root node as having more ancestral character states. Despite the ubiquity of the usage of basal , systematists try to avoid its usage because its application to extant groups

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1312-467: The more quadrupedally adapted Scelidosaurus may have been bipedal for some of the time, particularly as a juvenile. Stegosaurs and ankylosaurs are thought to have been obligately quadrupedal. While ranked taxonomy has largely fallen out of favor among dinosaur paleontologists, a few 21st century publications have retained the use of ranks, though sources have differed on what its rank should be. Most have listed Thyreophora as an unranked taxon containing

1353-419: The root of every cladogram, those clades may differ widely in taxonomic rank , species diversity , or both. If C is a basal clade within D that has the lowest rank of all basal clades within D , C may be described as the basal taxon of that rank within D . The concept of a ' key innovation ' implies some degree of correlation between evolutionary innovation and diversification . However, such

1394-423: The root than the majority, and in such cases, expressions like "very basal" can appear. A 'core clade' refers to the grouping that encompasses all constituent clades except for the basal clade(s) of the lowest rank within a larger clade, exemplified by core eudicots . No extant taxon is closer to the root than any other. A basal group in the stricter sense forms a sister group to the rest of the larger clade, as in

1435-529: The sister group of a more species-rich clade displays ancestral features. An extant basal group may or may not resemble the last common ancestor of a larger clade to a greater degree than other groups, and is separated from that ancestor by the same amount of time as all other extant groups. However, there are cases where the unusually small size of a sister group does indeed correlate with an unusual number of ancestral traits, as in Amborella (see below). This

1476-404: The skin), with these osteoderms having lateral keels. Characters of the skull and jaws distinctive ( synapomorphic ) of thyreophorans include "absence of a deep elliptic fossa along the sutural line of the nasals , presence of a wide jugal , remodeling of skull dermal bone , down-turned dentary tooth row". Among primitive thyreophorans, Scutellosaurus was likely primarily bipedal, while

1517-431: The study naming the genus, by Sergio Soto-Acuña and colleagues, coined Parankylosauria based on the two aforementioned genera and Kunbarrasaurus . The name, referencing its parent group, means "at the side of Ankylosauria". The Parankylosauria may not have been the only Gondwanan ankylosaurians; Patagopelta was described from Argentina in 2022, and has been found to be closely allied with North American nodosaurids in

1558-580: The subfamily Nodosaurinae . This would suggest that in addition to the more ancient Parankylosauria, more derived euankylosaurians also inhabited South America, having migrated from North America as part of a biotic interchange during the Campanian . However, more recent studies have suggested a parankylosaur affinity for Patagopelta . Known members of Parankylosauria are all small animals, ranging from 1.5–4.0 metres (4.9–13.1 ft), and possessed proportionally large skulls. The most distinctive trait of

1599-565: The traditional suborders Stegosauria and Ankylosauria, though Thyreophora is also sometimes classified as a suborder, with Ankylosauria and Stegosauria as infraorders. Thyreophora was first named by Nopcsa in 1915. Thyreophora was defined as a clade by Paul Sereno in 1998, as "all genasaurs more closely related to Ankylosaurus than to Triceratops ". Thyreophoroidea was first named by Nopcsa in 1928 and defined by Sereno in 1986, as " Scelidosaurus , Ankylosaurus , their most recent common ancestor and all of its descendants". Eurypoda

1640-526: Was first named by Sereno in 1986 and defined by him in 1998, as " Stegosaurus , Ankylosaurus , their most recent common ancestor and all of their descendants". In 2021, an international group of researchers led by Daniel Madzia registered almost all of the most commonly used ornithischian clades under the International Code of Phylogenetic Nomenclature , with the intent of standardizing their definitions. According to Madzia et al. , Thyreophora

1681-425: Was questioned if they might instead belong to a marine reptile , which would make the genus based on a chimeric specimen. The discovery of the genus Stegouros , published and named in 2021, helped to clear up the previous confusion. The type specimen of the genus preserved enough of the skeleton to make it clear that there was a previously unrecognized monophyletic grouping of these southern ankylosaur taxa. Thus

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