Nodosauridae is a family of ankylosaurian dinosaurs known from the Late Jurassic to the Late Cretaceous periods in what is now Asia, Europe, North America, and possibly South America. While traditionally regarded as a monophyletic clade as the sister taxon to the Ankylosauridae, some analyses recover it as a paraphyletic grade leading to the ankylosaurids.
Description
Nodosaurids, like their sister group the ankylosaurids, were heavily armored dinosaurs adorned with rows of bony armor nodules and spines (osteoderms), which were covered in keratin sheaths. Ankylosaurians were small- to large-sized, heavily built, quadrupedal, herbivorous dinosaurs, possessing small, leaf-shaped teeth. Unlike ankylosaurids, nodosaurids lacked mace-like tail clubs and instead had more flexible tail tips. Many nodosaurids had spikes projecting outward from their shoulders. One particularly well-preserved nodosaurid "mummy", the holotype of Borealopelta markmitchelli, preserves a nearly complete set of armor in life position, as well as the keratin covering and mineralized remains of the underlying skin, which indicate reddish pigments in a countershading pattern.
Classification The family Nodosauridae was erected by Othniel Charles Marsh in 1890, and anchored on the genus Nodosaurus. The clade Nodosauridae was first informally defined by Paul Sereno in 1998 as "all ankylosaurs closer to Panoplosaurus than to Ankylosaurus," a definition followed by Vickaryous, Teresa Maryańska, and Weishampel in 2004. Vickaryous et al. considered two genera of nodosaurids to be of uncertain placement (incertae sedis): Struthiosaurus and Animantarx, and considered the most primitive member of the Nodosauridae to be Cedarpelta. Following the publication of the PhyloCode, Nodosauridae needed to be formally defined following certain parameters, including that the type genus Nodosaurus was required as an internal specifier. In formally defining Nodosauridae, Madzia and colleagues followed the previously established use for the clade, defining it as the largest clade including Nodosaurus textilis but not Ankylosaurus magniventris. As all phylogenies referenced included both Panoplosaurus and Nodosaurus within the same group relative to Ankylosaurus, the addition of another internal specifier was deemed unnecessary. Nodosauridae is traditionally composed of the basal clade Polacanthinae (sometimes recovered outside of the Nodosauridae), as well as the Panoplosaurini and Struthiosaurini within the Nodosaurinae. Nodosaurinae is defined in the PhyloCode as "the largest clade containing Nodosaurus textilis, but not Hylaeosaurus armatus, Mymoorapelta maysi, and Polacanthus foxii". Panoplosaurini is defined in the PhyloCode as "the largest clade containing Panoplosaurus mirus, but not Nodosaurus textilis and Struthiosaurus austriacus" while Struthiosaurini has a similar definition of "the largest clade containing Struthiosaurus austriacus, but not Nodosaurus textilis and Panoplosaurus mirus". Topology A below demonstrates these relationships, following the phylogenetic analyses of Rivera-Sylva and colleagues (2018), with clade names added by definition from Madzia et al. (2021). However, in 2023, Raven and colleagues proposed an alternate phylogeny for nodosaurids; instead of the traditional dichotomous split between nodosaurids and ankylosaurids, their analyses resulted in a paraphyletic grade of these taxa comprising the monophyletic clades Panoplosauridae, Polacanthidae and Struthiosauridae. These results are displayed in Topology B below. Corresponding clades are shown in matching colors for clarity, and ⊞ buttons can be clicked to expand nodes:
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