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Clade
Subclade

Taxon
Taxon
Hadrosauridae
Nominal Author
Cope 1869
2nd Nominal Author
Taxon Status ACTIVE
Comments

Hadrosauridae has been used variosuly to include two or more subfamilies (Lambeosaurinae, Hadrosaurinae) as well as well as several genera that might lie outside these, such as Telmatosaurus Weishampel et al. (1990, 1993) or Protohadros (Head 1998). Their trait-based diagnoses differed one to the next, in their attempts to include these less well known basal taxa. Thus Weishampel et al. (1990:534) listed 11 synapomorphies; Weishampel et al. (1993: 375) listed seven, only four of which were listed in 1990; Head (1998:fig. 15) listed those same four but for a clade that now included a new basal taxon, Protohadros. Head (1998) also inserted Bactrosaurus as the sister taxon of Lambeosaurinae, which together formed the sister taxon to Hadrosaurinae. The position of basal taxa, however, has been based largly on cranial evidence and subject to change. Shortly thereafter, Godefroit et al. (1998) placed Bactrosaurus in a more basal position, based on better preserved remains (acknowledged in an addendum in Head, 1998).

Hadrosauridae, thus, was being handled as a trait-based taxon that incorporated new basal genera as they appeared; Weishampel et al. (1993; see also Weishampel et al. 2004) erected a new taxon, Euhadrosauria, to encompass “the traditional groupings of lambeosaurines and hadrosaurines”. This contravenes traditional taxonomy, as it constitutes a taxon within the family group (i.e. within Hadrosauridae) without any family-group suffix.

Norman (1998, 2002) offered new variations on the taxonomic scope of both Euhadrosauria and Hadrosaruidae. In 1998, he diagnosed Euhadrosauria with characters previously used for Hadrosauridae, such as “miniaturization of the teeth,” and placed it on a cladogram in a position noremally reserved for Hadrosauridae (Norman 1998:fig. 35). Later, Norman (2002:fig. 35) placed Hadrosauridae in a position on a cladogram that excluded Protohadros, the basalmost taxon in Head’s (1998) version of Hadrosaruidae. None of these authors presented phylogenetic definitions for either Hadrosauridae or Euhadrosauria.

Forster (1997) and Sereno (1997, 1998, 1999a, b), in contrast, concluded that it would be easier and more reflective of historical practice to define Hadrosauridae as a node-based taxon composed of stem-based Lambeosaurinae and Hadrosaurinae. Godefroit et al. (1998) determined the same hierarchy, which identifies a major split in the evolution of advanced ornithopods. Although Horner et al. (2004:438) stated that “Weishampel et al. (1993) presented what amounts to the first formal node-based definition of Hadrosauridae,” there were no phylogenetic definitions in that paper and the cited definition (“Telmatosaurus and Parasaurolophus [sic] plus all of the descendants of this common ancestor”) is a modification of that proposed by Sereno (1998; “Saurolophus, Parasaurolophus, their most recent common ancestor and all descendants”).

In short, there is no advantage to placing Hadrosauridae among a graded series of stems rather than to recognize with a node-stem triplet a dichotomy that has long been a part of traditional taxonomy. The active definition is a first-order revision of the definition in Sereno (1998). It uses well-preserved, nested species as specifiers and includes the eponymous genus Hadrosaurus as a positive taxon qualifier.

Potential Synonomy

Active Phylogenetic Definition
Active Definition
The least inclusive taxon containing Saurolophus osborni Brown 1912 and Parasaurolophus walkeri Parks 1922 and including Hadrosaurus foulkii Leidy 1858.
Shorthand
< Saurolophus osborni and Parasaurolophus walkeri + Hadrosaurus foulkii.
Definitional Author
Sereno 2005
Definition Status checked
Definition Type NODE
Node-Stem Triplet NODE
Other Triplet Taxa
Hadrosaurinae, Lambeosaurinae
Specifiers
Specifier(s) A
Specifier(s) B
Specifier(s) C
Qualifiers
+Taxon
Hadrosaurus foulkii
-Taxon
Datum
Taxonomic Content
Publication Year Unknown
Unknown
Unknown
1997

Inactive Taxon Status
Rejection Criteria
Critique
 

Definitional History #1
Earliest Record
Lambeosaurinae plus Hadrosaurinae and their most recent common ancestor.
Latest Record
Forster 1997:47A
Range (My)
Range (My)
Lambeosaurinae, Hadrosaurinae
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Definitional History #2
Earliest Record
Saurolophus, Parasaurolophus, their most recent common ancestor and all descendants.
Latest Record
Sereno 1998:62
Range (My)
Range (My)
Saurolophus, Parasaurolophus
Range (My)

Definitional History #3
Earliest Record
The most recent common ancestor of Telmatosaurus and Parasaurolophus plus all the descendants of this common ancestor.
Latest Record
Horner et al. 2004:438
Range (My)
Range (My)
Telmatosaurus, Parasaurolophus
Range (My)

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Definitional History #10
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