<documentid="6CB33737C9D174AE59B9E57D9A3812D1"ID-CLB-Dataset="34542"ID-DOI="http://dx.doi.org/10.3897/zookeys.223.2840"ID-GBIF-Dataset="b9b1f5ed-fec1-474c-a014-f0fbb309f54b"ID-PMC="PMC3491919"ID-Pensoft-Pub="1313-2970-226-1"ID-PubMed="23166462"ModsDocAuthor=""ModsDocDate="2012"ModsDocID="1313-2970-226-1"ModsDocOrigin="ZooKeys 226"ModsDocTitle="Taxonomy, morphology, masticatory function and phylogeny of heterodontosaurid dinosaurs"checkinTime="1451248705912"checkinUser="pensoft"docAuthor="Sereno, Paul C."docDate="2012"docId="A005FC2D67BE66C0B726BA78F76872EE"docLanguage="en"docName="ZooKeys 226: 1-225"docOrigin="ZooKeys 226"docSource="http://dx.doi.org/10.3897/zookeys.223.2840"docTitle="Fruitadens haagarorum Butler et al. 2010"docType="treatment"docVersion="6"lastPageNumber="29"masterDocId="FFFCFF9FFF9B1434FFE8FF88BA74FFB7"masterDocTitle="Taxonomy, morphology, masticatory function and phylogeny of heterodontosaurid dinosaurs"masterLastPageNumber="225"masterPageNumber="1"pageNumber="26"updateTime="1732745553822"updateUser="ExternalLinkService">
<taxonomicNameid="96BB4BFE010A7301A880E7019A200962"LSID="http://species-id.net/wiki/Fruitadens_haagarorum"authority="Butler et al., 2010"authorityName="Butler et al."authorityYear="2010"genus="Fruitadens"lsidName="Fruitadens haagarorum"pageId="25"pageNumber="26"rank="species"species="haagarorum">
<bibRefCitationid="7BFE7D36AC83A958F2E4893BCBF90962"author="Callison, G"journalOrPublisher="Journal of Systematic Palaeontology"pageId="161"pageNumber="162"title="Tiny dinosaurs: are they fully grown? Journal of Vertebrate Paleontology 3: 200 - 209."url="10.1080/02724634.1984.10011975"year="1984">Callison and Quimby (1984</bibRefCitation>
<bibRefCitationid="EC499F134BDF43DA09F05A9E8BF012AD"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"pagination="375 - 381"title="Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America."url="10.1098/rspb.2009.1494"volume="277"year="2010">Butler et al. (2010</bibRefCitation>
<bibRefCitationid="51E52E7EF63D77A41DC63219860E08C7"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"title="Anatomy and cranial functional morphology of the small-bodied dinosaur Fruitadens haagarorum from the Upper Jurassic of the USA. PLoS One 7: e 31556."url="10.1371/journal.pone.0031556."year="2012">Butler et al. (2012</bibRefCitation>
LACM 115747, adult with partial maxillae and dentaries, cervical, dorsal, sacral and caudal vertebrae, proximal right femur, proximal and distal ends of the tibiae, and partial right metatarsal 1 (
<bibRefCitationid="1D23CBE555E857366E7ACAF07D25C6C4"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"pagination="375 - 381"title="Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America."url="10.1098/rspb.2009.1494"volume="277"year="2010">Butler et al. 2010</bibRefCitation>
<bibRefCitationid="44BFE141A768F2F49B05CF8D0A4DBBC6"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"title="Anatomy and cranial functional morphology of the small-bodied dinosaur Fruitadens haagarorum from the Upper Jurassic of the USA. PLoS One 7: e 31556."url="10.1371/journal.pone.0031556."year="2012">Butler et al. 2012</bibRefCitation>
LACM 115727, adult partial postcranial skeleton with partial cervical, dorsal and caudal vertebrae, partial right and left femora, and an articulated distal left tibia and coossified astragalocalcaneum; LACM 120478, subadult with left humerus, distal left femur, and an articulated left tibia, fibula and coossified astragalocalcaneum; LACM 120602, distal caudal vertebra, left astragalocalcaneum, partial metatarsus and pes; LACM 128258, subadult with right premaxilla, partial left maxilla, partial left and right dentaries, and one dorsal and one distal caudal vertebra; LACM 128303, anterior left dentary (
<bibRefCitationid="8CFFBD86918E2C340A636789C8420243"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"pagination="375 - 381"title="Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America."url="10.1098/rspb.2009.1494"volume="277"year="2010">Butler et al. 2010</bibRefCitation>
<bibRefCitationid="3E7C221A87E20045A9D91FBA163A77E2"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"title="Anatomy and cranial functional morphology of the small-bodied dinosaur Fruitadens haagarorum from the Upper Jurassic of the USA. PLoS One 7: e 31556."url="10.1371/journal.pone.0031556."year="2012">2012</bibRefCitation>
<paragraphid="0F300EFD255A4CB32A5E2CD9F8643E9B"pageId="25"pageNumber="26">Heterodontosaurid with (1) a discordantly small dentary tooth immediately distal to the caniniform dentary tooth and (2) a prominent anteromedial flange on the distal end of the tibia.</paragraph>
<bibRefCitationid="3BB4F2B9E6E116BB78906B0D32B706E1"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"pagination="375 - 381"title="Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America."url="10.1098/rspb.2009.1494"volume="277"year="2010">Butler et al. (2010</bibRefCitation>
<bibRefCitationid="B70D413588103E59DAC614A2F9397969"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"title="Anatomy and cranial functional morphology of the small-bodied dinosaur Fruitadens haagarorum from the Upper Jurassic of the USA. PLoS One 7: e 31556."url="10.1371/journal.pone.0031556."year="2012">Butler et al. (2012</bibRefCitation>
This suite of features constitutes a differential diagnosis-a unique combination of the features that describes a monospecific genus rather than a set of autapomorphies hypothesized to have arisen in the immediate ancestry of the taxon (
<bibRefCitationid="E449E0CB9504F6527DD781E59A0E11A0"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"pagination="375 - 381"title="Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America."url="10.1098/rspb.2009.1494"volume="277"year="2010">Butler et al. 2010</bibRefCitation>
<bibRefCitationid="9C031D1717A199A9E52F6ED0822EC255"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"title="Anatomy and cranial functional morphology of the small-bodied dinosaur Fruitadens haagarorum from the Upper Jurassic of the USA. PLoS One 7: e 31556."url="10.1371/journal.pone.0031556."year="2012">Butler et al. (2012)</bibRefCitation>
<bibRefCitationid="70C7E1986A794A9BBFAED7E3B5F421E5"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"title="Anatomy and cranial functional morphology of the small-bodied dinosaur Fruitadens haagarorum from the Upper Jurassic of the USA. PLoS One 7: e 31556."url="10.1371/journal.pone.0031556."year="2012">Butler et al. 2012</bibRefCitation>
One dental feature listed in the revised diagnosis may be an autapomorphy but is homoplasious among heterodontosaurids. The dentary tooth immediately distal to the caniniform tooth in
<bibRefCitationid="816E1BF7194B38E32C180D37B18EC1A1"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"pagination="375 - 381"title="Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America."url="10.1098/rspb.2009.1494"volume="277"year="2010">Butler et al. (2010</bibRefCitation>
<bibRefCitationid="CCD8C0C441136E9FE2D0B26D819ABD4B"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"title="Anatomy and cranial functional morphology of the small-bodied dinosaur Fruitadens haagarorum from the Upper Jurassic of the USA. PLoS One 7: e 31556."url="10.1371/journal.pone.0031556."year="2012">2012</bibRefCitation>
. The dentary caniniform tooth was said to be shorter than in some heterodontosaurids and more nearly equal in depth to noncaniniform dentary crowns. The relative depth of individual crowns, however, depends to a great extent on the stage of replacement, which can be difficult to estimate in the case of caniniform teeth. The dentary caniniform tooth in the Kayenta heterodontosaurid, for example, has a similar relative depth to that in
, although it is clearly undergoing eruption and would be considerably larger when fully functional (Fig. 9A, B). Most of the caniniform tooth in question (LACM 128258), furthermore, seems to have broken away by the time the specimen was described by
<bibRefCitationid="93D05A7D63551F432052AA47ECAE8FA8"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"pagination="375 - 381"title="Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America."url="10.1098/rspb.2009.1494"volume="277"year="2010">Butler et al. (2010</bibRefCitation>
The separation of the ascending process of the astragalus as a separate ossification was listed among the autapomorphies. The suture separating the distal tip of the astragalar ascending process, however, seems to continue laterally as a fracture line across the distal shaft of the fibula. The ascending process had been viewed as a separate ossification in the theropod
(Welles 1984); review of this specimen, however, suggests that it also appears to be a postmortem fracture passing through vascular foramina. Persistence of such a suture in
were collected between 1975 and 1980 in the Fruita Paleontological Area from four separate localities above a distinctive horizon ("clay change") near the base of the Brushy Basin Member of the Morrison Formation (
). The localities were not discovered in a single horizon but rather within a zone perhaps 10-15 m in thickness above the "clay change" (G. Callison, pers. comm.). Four specimens were described in the initial description (
<bibRefCitationid="AD3F00B03DE6FA6997C26E06679D656B"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"pagination="375 - 381"title="Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America."url="10.1098/rspb.2009.1494"volume="277"year="2010">Butler et al. 2010</bibRefCitation>
<bibRefCitationid="87606FAFB61821B58FA59E3A8A9C33DF"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"title="Anatomy and cranial functional morphology of the small-bodied dinosaur Fruitadens haagarorum from the Upper Jurassic of the USA. PLoS One 7: e 31556."url="10.1371/journal.pone.0031556."year="2012">Butler et al. 2012</bibRefCitation>
(Table 3). The sole specimen known of the Kayenta heterodontosaurid is the smallest heterodontosaurid on record (skull length estimate of 53 mm), but histologic evidence suggests that it is a subadult roughly the same size as half-grown individuals of
and three referred specimens were described as associated individuals, the supportive evidence limited to the lack of duplicate bones and consistent state of preservation within each specimen (
<bibRefCitationid="08E156E2CE0A0611035A37411352103F"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"pagination="375 - 381"title="Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America."url="10.1098/rspb.2009.1494"volume="277"year="2010">Butler et al. 2010</bibRefCitation>
<bibRefCitationid="603285EE300725100D6C0C3AD3BE51EF"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"title="Anatomy and cranial functional morphology of the small-bodied dinosaur Fruitadens haagarorum from the Upper Jurassic of the USA. PLoS One 7: e 31556."url="10.1371/journal.pone.0031556."year="2012">Butler et al. 2012</bibRefCitation>
). A first-hand account of the discovery of the holotype (LACM 115747) and a referred subadult specimen (LACM 120478) confirms their association as individuals. The first pieces of the holotype were surface-collected on a slope, which led to an in situ portion of the specimen that was recovered in a small field jacket (G. Callison, pers. comm.). The subadult specimen LACM 120478, which preserves the most complete long bone lengths, was also found in a confined space by quarrying at a nearby locality 5572 ("Main Callison Quarry"). A referred adult specimen was found at locality 5576 (
Coelurosaur site"), and there is no specific site information available for a referred subadult with the most complete set of jaws (LACM 128258), except that it comes from the same general area (Fruita Paleontological Area).
has a vascularized buccal emargination, presumably as an aid to the processing plant materials within the oral cavity (Fig. 9A). The anterior end of the dentary in
<bibRefCitationid="CDD5C6532BB60791466D60E83164F994"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"pagination="375 - 381"title="Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America."url="10.1098/rspb.2009.1494"volume="277"year="2010">Butler et al. 2010</bibRefCitation>
: fig. 2a). Only the middle tooth preserves the entire crown; only the base of the distal crown is preserved, and the first crown in the series appears to have been lost.
<bibRefCitationid="4CD07972C20AD0949D076F0F8B12B7DC"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"pagination="375 - 381"title="Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America."url="10.1098/rspb.2009.1494"volume="277"year="2010">Butler et al. (2010</bibRefCitation>
<bibRefCitationid="141AFDA0D8131E0BF00A661A7A72EF43"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"title="Anatomy and cranial functional morphology of the small-bodied dinosaur Fruitadens haagarorum from the Upper Jurassic of the USA. PLoS One 7: e 31556."url="10.1371/journal.pone.0031556."year="2012">Butler et al. (2012)</bibRefCitation>
, further, suggested that a small portion of the left premaxilla might be attached across the median palatal suture. A portion of an ascending ramus has been shown as preserved on the premaxilla (Fig. 9A), but no part of this ramus appears to be preserved on the actual specimen (
<bibRefCitationid="B68C117CFB43E0D4955B5480EEFC9A15"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"title="Anatomy and cranial functional morphology of the small-bodied dinosaur Fruitadens haagarorum from the Upper Jurassic of the USA. PLoS One 7: e 31556."url="10.1371/journal.pone.0031556."year="2012">Butler et al. 2012</bibRefCitation>
the narial fossa is not evident in lateral view. The identification of this jaw fragment as a portion of the right premaxilla may be correct, but it exhibits several unusual features as compared to more completely known premaxillae in
has a deep margin between the antorbital fenestra and the maxillary tooth row, although this depth can appear greater with postmortem compression (Fig. 9A). As preserved it most closely resembles the condition in
<bibRefCitationid="34CC9E578B781C701F1FF1F3D109CB9C"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"pagination="375 - 381"title="Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America."url="10.1098/rspb.2009.1494"volume="277"year="2010">Butler et al. (2010</bibRefCitation>
<bibRefCitationid="081344FEA8A1CD32D8E371131DFF847F"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"pagination="375 - 381"title="Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America."url="10.1098/rspb.2009.1494"volume="277"year="2010">Butler et al. 2010</bibRefCitation>
<bibRefCitationid="C0445A7C462E7FA70A672A1F3588F387"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"pagination="375 - 381"title="Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America."url="10.1098/rspb.2009.1494"volume="277"year="2010">Butler et al. 2010</bibRefCitation>
<bibRefCitationid="9A4A0208CD03D37B1B0951668DAE96DF"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"pagination="375 - 381"title="Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America."url="10.1098/rspb.2009.1494"volume="277"year="2010">Butler et al. 2010</bibRefCitation>
<bibRefCitationid="982F391E8455FFA6DBD05CD0575CF6B1"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"pagination="375 - 381"title="Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America."url="10.1098/rspb.2009.1494"volume="277"year="2010">Butler et al. (2010)</bibRefCitation>
<bibRefCitationid="D57D25139E6BAE7C06B543C6115A202A"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"pagination="375 - 381"title="Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America."url="10.1098/rspb.2009.1494"volume="277"year="2010">Butler et al. 2010</bibRefCitation>
: fig. 2.7C, F, G). The apical edge of the cingulum is maintained in the center of the crown base, where the median eminence joins the base of the crown (Fig. 9A). This well-defined cingulum is present only in the largest crowns and resembles the condition in the cheek teeth of thyreophoran ornithischians. A similar condition is present in
<bibRefCitationid="D18FB0149ABAEA84BF88AEE0EC81BC0A"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"pagination="375 - 381"title="Lower limits of ornithischian dinosaur body size inferred from a new Upper Jurassic heterodontosaurid from North America."url="10.1098/rspb.2009.1494"volume="277"year="2010">Butler et al. 2010</bibRefCitation>
<bibRefCitationid="91B5070DA2084DAEF86D396FAF5DBBBD"author="Butler, RJ"journalOrPublisher="Proceedings of the Royal Society B: Biological Sciences"pageId="161"pageNumber="162"title="Anatomy and cranial functional morphology of the small-bodied dinosaur Fruitadens haagarorum from the Upper Jurassic of the USA. PLoS One 7: e 31556."url="10.1371/journal.pone.0031556."year="2012">Butler et al. 2012</bibRefCitation>
to-tooth occlusion, however, have not been identified. The presence or absence of wear facets is difficult to determine with so few available crowns. Some of these specimens, in addition, are from younger individuals, which may not show wear typical of adults. The low-angle wear facets in
