Proceratosauridae
Family of small, long-armed tyrannosauroid dinosaurs.
Proceratosauridae is a group of tyrannosauroid theropods that lived from the Middle Jurassic into the Early Cretaceous. Most members were small, with long, three-fingered arms suited for grabbing prey—similar to early tyrannosauroids like *Dilong* but unlike later, more advanced tyrannosaurids. Two possible exceptions are *Yutyrannus* and *Sinotyrannus*, which may have been larger. The family was established in 2010 by Oliver Rauhut and his team during their reassessment of the type genus, *Proceratosaurus*.
Several skeletal traits set proceratosaurids apart from other tyrannosauroids, based on studies from 2010 and 2013. These include a crest on the skull formed by the nasal bones, beginning where the premaxilla meets the nasals; very long nostrils that extend backward past the front edge of the antorbital fossa and maxillary openings; a short lower edge of the premaxilla; a deep section of the antorbital fossa below the antorbital fenestra, much deeper than the maxilla beneath it; a concave ischium; a convex bump on the front of the pubis just below its contact with the ilium; and a short, shallow notch on the front edge of the maxilla.
The family sits within or near the tyrannosaur lineage. Rauhut and colleagues originally defined the clade as all theropods closer to *Proceratosaurus* than to *Tyrannosaurus*, *Allosaurus*, *Compsognathus*, *Coelurus*, *Ornithomimus*, or *Deinonychus*. Their work supported *Proceratosaurus* as a coelurosaur and tyrannosauroid, with its closest relative being the Chinese *Guanlong*. Later studies added *Kileskus* from Russia and *Sinotyrannus* from China. By the mid-2010s, the family was thought to include *Proceratosaurus*, *Guanlong*, *Kileskus*, *Sinotyrannus*, and also *Stokesosaurus*, *Juratyrant*, and *Dilong*—genera once considered non-proceratosaurid tyrannosauroids. Rauhut’s team also noted that teeth from the Late Jurassic and Early Cretaceous, previously assigned to the dromaeosaurid subfamily Velociraptorinae, might actually belong to proceratosaurids, because the teeth look alike and velociraptorines are not otherwise known until the Late Cretaceous. This means that *Nuthetes* and other poorly known genera could be proceratosaurids.
A 2013 cladogram by Loewen and colleagues shows one proposed family tree.
Quick Facts
- Taxon
- Proceratosauridae
- Type Species
- Proceratosaurus bradleyi
- Type Species Authority
- Woodward, 1910
Facts from the source article.
Lore & Background
Proceratosauridae was first named in 2010 by Oliver Rauhut and colleagues in their re-evaluation of the type genus, Proceratosaurus. Their study supported the idea that Proceratosaurus is a coelurosaur, a tyrannosauroid, and most closely related to the Chinese tyrannosauroid Guanlong. They defined the clade containing these two dinosaurs as all theropods closer to Proceratosaurus than to Tyrannosaurus, Allosaurus, Compsognathus, Coelurus, Ornithomimus, or Deinonychus. Later studies included the Russian Kileskus and the Chinese Sinotyrannus in the family.
Reader's Guide
Proceratosauridae represents an early branch of the tyrannosauroid lineage, providing insight into the evolution of later, larger tyrannosaurids. Their distinguishing features include a sagittal cranial crest formed by the nasals, extremely elongated external nares, a short ventral margin of the premaxilla, and a ventrally concave ischium. By the mid-2010s, the family was considered to include Proceratosaurus, Guanlong, Kileskus, Sinotyrannus, and the genera Stokesosaurus, Juratyrant, and Dilong previously recognized as non-proceratosaurid tyrannosauroids. An analysis by Brusatte et al. in 2016 placed Yutyrannus within Proceratosauridae as a sister taxon to Sinotyrannus, while Juratyrant and Stokesosaurus were placed as more advanced tyrannosauroids. In 2025, Delcourt et al. found Proceratosauridae as early-diverging maniraptoromorphs outside Tyrannosauroidea, highlighting ongoing taxonomic debate.
Did You Know?
- The family includes the genera Proceratosaurus, Guanlong, Kileskus, and Sinotyrannus.
- Some tooth taxa from the Late Jurassic and Early Cretaceous previously assigned to Velociraptorinae may instead be proceratosaurid.
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