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Andrew Heckert

Appalachian State University, Geology, Faculty Member

North Carolina State Museum of Natural Sciences, Paleontology, Department Member

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PhD University of New Mexico 2001
MS University of New Mexico 1997
BS Denison University 1993 Summa cum laude

Vertebrate paleontologist principally interested in Triassic microvertebrates, Late Triassic ecosystems, archosaur teeth and dentitions, and a range of other Mesozoic topics.
Address: Dept. Geology ASU Box 32067
572 Rivers St
Appalachian State University
Boone, NC 28608-2067

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University of New England - Australia

Michael Brett-Surman

Steven Jasinski

University of Pennsylvania

Steven E Jasinski

State Museum of Pennsylvania

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Papers by Andrew Heckert

Cretaceous dinosaurs in New Mexico

New Mexico's most extensive fossil record of dinosaurs is from rocks of Cretaceous age. The Early... more New Mexico's most extensive fossil record of dinosaurs is from rocks of Cretaceous age. The Early Cretaceous record is confined to tracks of late Albian age, principally from northeastern NM. They are primarily of ornithopods (Caririchnium, Amblydactylus) and lesser numbers of theropods. They provide circumstantial evidence of social behavior in ornithopods and, because of the lack of sauropod tracks, suggest the extirpation of North American sauropods took place during the late Albian. New Mexico's record of Late Cretaceous dinosaurs includes a few tracksites (notably including the holotype of Tyrannosauripus from the late Maastrichtian of the Raton basin) and an extensive body fossil record from rocks of late Turonian, late Santonian, Campanian and Maastrichtian age. Highlights of this record include: (1) Zuniceratops from the late Turonian Moreno Hill Formation, the oldest North American ceratopsian with brow horns, which suggests a possible North American origin of ceratopsids; (2) hadrosaur, ceratopsian and theropod fossils from the late Santonian Crevasse Canyon Formation and early Campanian Menefee Formation that are mostly fragmentary and isolated but that indicate a need to collect further this largely unsampled interval; (3) an extensive late Campanian record from the Fruitland and Kirtland formations in the San Juan Basin that provides strong evidence of Asian-North American interchange of Campanian dinosaurs; and (4) a possible Paleocene dinosaur record from the San Juan Basin.

Stratigraphy, taphonomy, and new discoveries from the Upper Jurassic (Morrison Formation: Brushy Basin Member) Peterson quarry, central New Mexico

The Upper Jurassic Peterson quarry, located in Bernalillo County, central New Mexico, is New Mexi... more The Upper Jurassic Peterson quarry, located in Bernalillo County, central New Mexico, is New Mexico's most extensive and productive Jurassic dinosaur locality. The quarry is developed in the upper Brushy Basin Member of the Morrison Formation, approximately 26 m below its contact with the overlying Jackpile Member. Bones occur low in a 3.3-m-thick sequence of well-indurated, troughcrossbedded, subarkosic sandstone. Preserved elements range from scattered bones to articulated assemblages of bones from a single individual, and the long bones are preferentially oriented along a generally east-west-trending axis. The occurrence of associated-to-articulated bones in a troughcrossbedded sandstone underlying a floodplain mudstone suggests deposition of the fossils in the mixed fill of an abandoned channel in a typical Brushy Basin Member fluvial system. Particularly important dinosaurs from the Peterson quarry include a large (1100 mm estimated. femoral length) Saurophaganax-like allosaurid theropod and the anterior portion of a diplodocid skull and lower jaws similar to Diplodocus. This specimen is one of less than a dozen Morrison Formation diplodocid skulls known and is particularly important because it is: (1) the only Jurassic sauropod skull material from New Mexico; (2) could represent a genus and/or species of Morrison diplodocid from which skull material is not yet known; and (3) provides insight into the replacement pattern of diplodocid teeth. FIGURE 3. Photographs of the Peterson quarry. A, Overview of the quarry on 18 July 1999. The principal bonebed is the arroyo bottom partially filled with water. B, View in the quarry on 2 July 1995 showing trough-crossbedded, channelform sandstone geometry of bone-bearing sandstone interval; man on left is covering a pedestaled bone. C, Sauropod tibia and fibula in the quarry, 16 May 1999. D, Articulated theropod bones in the quarry, 22

A Revueltian (Norian) phytosaur from the Sonsela Member of the Petrified Forest Formation (Chinle Group: Upper Triassic), Petrified Forest National Park, Arizona

The Sonsela Member of the Petrified Forest Formation (Upper Triassic) is widely exposed in northe... more The Sonsela Member of the Petrified Forest Formation (Upper Triassic) is widely exposed in northeastern Arizona and northwestern New Mexico. Fossil wood is common in the fluvial Sonsela, but the high energy depositional conditions appear to have destroyed all fossil bone except for small fragments. The first identifiable vertebrate fossil from channel-facies of this unit is an incomplete phytosaur skull preserved on a fallen block of sandstone on a cliff in the Rainbow Forest area of Petrified Forest National Park, Arizona. This cliff is "Flattops Sandstone I," which we consider to represent the upper part of the Sonsela Member. The left side of the skull, lacking the anterior half of the rostrum, is preserved in lateral view. The specimen is uncollectable, but casts are preserved at Mesalands Dinosaur Museum, Petrified Forest National Park, and the New Mexico Museum of Natural History and Science. The two most important morphological features of this specimen are: (1) the external nares are at approximately the same level as the skull deck; and (2) the posterior squamosal process in lateral view is narrow and not pendulous. This combination of features is diagnostic of the genus Nicrosaurus. The only other published account of Nicrosaurus in North America is Nicrosaurus buceros from the Chama basin of north-central New Mexico. The common Nicrosaurus kapffi and the rare N. meyeri occur in the Norian Stubensandstein of southwestern Germany. This specimen is biochronologically sig:p.ificant as it demonstrates that the Sonsela is indeed Norian in age, as has been suggested previously. Paleobiogeographically, it is one of an increasing number of Late Triassic tetrapod taxa that were previously thought to be exclusively European in distribution (e.g., Erpetosuchus, Aetosaurus, Stagonolepis) that have now been identified in North America.

The microvertebrate fauna of the Upper Triassic (Revueltian) Snyder Quarry, north-central New Mexico

The Snyder quarry is a well-documented assemblage of Late Triassic invertebrates and vertebrates ... more The Snyder quarry is a well-documented assemblage of Late Triassic invertebrates and vertebrates from the Painted Desert Member of the Upper Triassic Petrified Forest Formation in the Chama Basin, north-central New Mexico. The presence of Revueltian index taxa, including the aetosaurs Typothorax coccinarum and Desmatosuchus chamaensis and the phytosaur Pseudopalatus buceros, demonstrate that the Snyder quarry is of Revueltian (early-mid Norian) age. Screenwashing matrix from the primary bonebed at the Snyder quarry yielded a moderately diverse assemblage of microvertebrates, some of which were not represented in the macrovertebrate fauna. Microvertebrate fossils from the Snyder quarry are mostly scales and bone fragments-complete teeth are unusually rare. New records include a tooth of the hybodontoid shark Lonchidion and numerous scales of a palaeoniscid fish tentatively assigned to aff. Turseodus. The microvertebrate assemblage differs somewhat from the known macrovertebrate assemblage, and includes many more osteichthyan fossils. Osteichthyans dominate the microvertebrate fauna, and include semionotids, redfieldiids, palaeoniscoids, and indeterminate sarcopterygians. Osteichthyans are largely represented by scales, with the exception of the indeterminate sarcopterygians and actinopterygians, represented by fragments of dentigerous toothplates, fossils previously assigned to "colobodontids." The microvertebrate tetrapod fauna represented by teeth includes metoposaurid amphibians, juvenile (?) phytosaurs (?), probable dinosaurs, aetosaurs and other diverse, unidentified archosauromorphs. Many of the vertebrae appear to pertain to small archosauromorphs. The microvertebrate assemblage is unusual in that recovered vertebrae and other non-cranial elements greatly outnumber intact teeth, which normally dominate Chinle microvertebrate assemblages. We interpret this as additional support for the hypothesis of a catastrophic origin for the Snyder quarry vertebrate assemblage, as more typical Chinle Group microvertebrate assemblages are attritional deposits in which teeth greatly outnumber vertebrae.

Triassic Dinosaurs in New Mexico

New Mexico has a sparse but growing record of Jurassic dinosaurs. The oldest records are theropod... more New Mexico has a sparse but growing record of Jurassic dinosaurs. The oldest records are theropod footprints and a sauropod vertebra from the Middle-Upper Jurassic Summerville Formation. The footprints are part of a widespread large theropod-pterosaur ichnofacies in the Summerville and equivalent strata in the southern Western Interior. The sauropod is one of the oldest North American sauropods. The oldest theropod eggshell is from the Upper Jurassic Morrison Formation in New Mexico. Most New Mexican Jurassic dinosaurs are from the Upper Jurassic Morrison Formation and include Apatosaurus, Diplodocus carnegiei, Diplodocus (=Seismosaurus) hallorum, Camarasaurus, Allosaurus, and Stegosaurus. These dinosaurs are part of a homogenous Morrison dinosaur chronofauna found throughout the Western Interior and characteristic of the Comobluffian land-vertebrate faunachron.

A new dinosaur footprint locality from the Dakota Sandstone (Upper Cretaceous: Cenomanian) in west-central New Mexico

We assign two incomplete dinosaur tracks from the Dakota Sandstone in Socorro County, west-centra... more We assign two incomplete dinosaur tracks from the Dakota Sandstone in Socorro County, west-central New Mexico to the ichnogenus Caririchnium sp., widely believed to represent the tracks of an iguanodontid ornithopod dinosaur. This is the first record of Cretaceous dinosaur tracks from west of the Rio Grande rift in New Mexico. Previous work suggests that the Dakota Sandstone in west-central New Mexico is of middle Cenomanian age, which makes these tracks younger than those of the so-called "dinosaur freeway" in the Dakota Group of northeastern New Mexico and eastern Colorado.

The tetrapod fauna of the Upper Triassic lower Chinle Group (Adamanian:latest Carnian), of the Zuni Mountains, west-central New Mexico

Numerous localities in the Bluewater Creek Formation in the Zuni Mountains of westcentral New Mex... more Numerous localities in the Bluewater Creek Formation in the Zuni Mountains of westcentral New Mexico produce a tetrapod fauna that includes the metoposaurid amphibian Buettnena sp., indeterminate phytosaurs, the aetosaurs Stagonolepis, Desmatosuchus, and Paratypothorax, two theropod dinosaurs, at least two ornithischian dinosaurs, including one identified here as aff. Tecovasaunls, and trace fossils consisting of a footprint of an ?ornithischian, and vertebrate coprolites. The most frequently encountered fossils are abundant cranial and postcranial fragments of metoposaurid amphibians and indeterminate phytosaurs. Stagonolepis is an index taxon of the Adamanian land-vertebrate faunachron, indicating that the Bluewater Creek Formation is latest Carnian in age, an observation consistent with abundant Desmatosuchus and large metoposaurid amphibians. The overlying Blue Mesa Member of the Petrified Forest Formation is relatively unfossiliferous in the Zuni Mountains, and has only produced fragmentary remains of indeterminate metoposaurs and phytosaurs, but produces an Adamanian fauna from various localities in Arizona. The dinosaur fauna from the Bluewater Creek Formation comes from a single locality, is the most diverse late Carnian dinosaur assemblage in North America, and includes some of the oldest known dinosaurs.

THE LATE TRIASSIC ARCHOSAUROMORPH <em>TRILOPHOSAURUS </em> AS AN ARBOREAL CLIMBER

DOAJ (DOAJ: Directory of Open Access Journals), Nov 1, 2005

Two species of the unusual archosauromorph Trilophosaurus, T. buettneri Case and T. jacobsi Murry... more Two species of the unusual archosauromorph Trilophosaurus, T. buettneri Case and T. jacobsi Murry, are known from diverse localities in the Upper Triassic Chinle Group in the southwestern USA. Both species likely occupied similar ecological niches, based on morphological similarities in the postcrania, which are essentially identical. Trilophosaurus occurrences in the Chinle Group are relatively rare, but individual sites are exceptionally rich, suggesting that Trilophosaurus lived in a different paleoenvironment than more typical Chinle vertebrates, which lived in or near streams (phytosaurs, metoposaurs) or on floodplains (aetosaurs, rauisuchians, and dinosaurs). Two potential interpretations are that Trilophosaurus was either an arboreal climber or a fossorial digger. However, the gross skeletal features of Trilophosaurus are not compatible with a fossorial mode of life: the limbs are too long and gracile, proximal limb elements are longer than distal ones, and the claws are laterally compressed, not transversely broadened. The intermittent study of Trilophosaurus has caused the theory of it being arboreal, originally proposed by Gregory, to receive little mention in subsequent studies. We reexamined the functional morphology of Trilophosaurus using a qualitative functional morphological analysis of the skeleton, a quantitative examination of claw curvature, and a quantitative examination of manus/trunk and pes/ trunk ratios. Claw morphology of Trilophosaurus shows similarities to the arboreal drepanosaurs Drepanosaurus and Megalancosaurus. Our analysis provides ample evidence to suggest that Trilophosaurus was arboreal. Riassunto. Nel Gruppo Chinle (Triassico Superiore) del Sudovest degli USA sono note due specie dell'insolito arcosauromorfo Trilophosaurus, T. buettneri Case e T. jacobsi Murry, provenienti da diverse localita Á . Probabilmente entrambe le specie occupavano nicchie ecologiche simili, sulla base di affinita Á morfologiche nelle ossa postcraniche, che sono sostanzialmente identiche. I ritrovamenti di Trilophosaurus nel Gruppo Chinle sono relativamente rari, ma singole localita Á possono essere significativamente ricche, suggerendo che Trilophosaurus vivesse in un ambiente diverso da quello dei tipici vertebrati della Chinle, che popolavano i fiumi o le loro vicinanze (fitosauri, metoposauri) o le piane alluvionali (aetosauri, rauisuchii e dinosauri). Due interpretazioni etologiche sono possibili, e cioe Á che Trilophosaurus fosse un arboricolo, oppure uno scavatore. Tuttavia le caratteristiche scheletriche principali di Trilophosaurus non sono compatibili con lo stile di vita di un fossatore: le zampe sono troppo lunghe e gracili, gli elementi prossimali delle zampe sono piu Á lunghi di quelli distali, e gli artigli sono compressi lateralmente e non allargati in senso trasversale. Essendo sporadici gli studi su Trilophosaurus l'interpretazione che fosse arboricolo, proposta inizialmente da Gregory, ricevette poca attenzione negli studi successivi. Noi abbiamo riesaminato la morfologia funzionale di Trilophosaurus utilizzando l'analisi qualitativa della morfologia funzionale dello scheletro, la valutazione quantitativa della curvatura degli artigli, e dei rapporti manus/tronco e pes/tronco. La morfologia degli artigli di Trilophosaurus mostra somiglianze con i drepanosauri arboricoli Drepanosaurus and Megalancosaurus. La nostra analisi fornisce ampie evidenze per sostenere che Trilophosaurus fosse arboricolo.

The microfauna of the Upper Triassic Ojo Huelos Member, San Pedro Arroyo Formation, central New Mexico, U.S.A

Three fossiliferous horizons at the type section of the Upper Triassic Ojo Huelos Member of the S... more Three fossiliferous horizons at the type section of the Upper Triassic Ojo Huelos Member of the San Pedro Arroyo Formation yield a microfauna of ostracodes, "spirorbids," sharks, bony fish, and tetrapods. These fossils represent a rare lacustrine microfossil assemblage near the base of the Upper Triassic Chinle Group. The fossiliferous interval consists primarily of pisolitic limestone and sandy mudstone. The fauna includes the ostracodes Darwinula sp., and Gerdalia sp., "spirorbid polychaetes," the hybodont shark Lissodus humblei, several morphotypes of actinopterygian fish, including redfieldiids and semionotids, fragmentary labyrinthodont amphibians, and indeterminate reptiles. Darwinula is the most common fossil. Numerically, Lissodus, known from dozens of teeth, dominates the vertebrate fauna, followed by actinopterygians. The smallest teeth of Lissodus from this locality are the smallest teeth known for the genus. This assemblage is consistent with an early Late Triassic (Carnian) age, and lithostratigraphic position suggests that this fauna is probably of Adamanian (latest Carnian) age. Carbonates of definitive lacustrine origin are rare in the Chinle, and this fauna documents the first discovery of microvertebrate tetrapods in lacustrine limestones of the Chinle Group. Because this microvertebrate fauna is clearly from an aquatic environment, this favors an aquatic (not scatologic) origin for similar fish-dominated microvertebrate faunas in the Chinle.

The Paleobiology of Coelophysis bauri (Cope) from the Upper Triassic (Apachean) Whitaker quarry, New Mexico, with detailed analysis

A new aetosaur (Archosauria: Pseudosuchia) from the upper Blue Mesa Member (Adamanian: Early–Mid Norian) of the Late Triassic Chinle Formation, northern Arizona, USA, and a review of the paratypothoracin <i>Tecovasuchus</i> across the southwestern USA

PaleoBios, Jul 17, 2023

Cover: Stratigraphic (A) and geographic occurrences (B) of the new typothoracine Kryphioparma cae... more

Ontogenetic heterodonty in<i>Reticulodus synergus</i>(Chondrichthyes, Hybodontiformes) from the Upper Triassic of the southwestern U.S.A., with a redescription of the genus

Journal of Vertebrate Paleontology, Jul 4, 2017

ABSTRACT Isolated teeth from the extinct hybodontoid Reticulodus synergus Murry and Kirby are kno... more ABSTRACT Isolated teeth from the extinct hybodontoid Reticulodus synergus Murry and Kirby are known from Upper Triassic strata of Revueltian age in Arizona, Utah, and New Mexico, U.S.A. Here, we provide evidence for ontogenetic heterodonty in Reticulodus based on a reappraisal of the type and newly discovered material from the Upper Triassic Bull Canyon Formation in east-central New Mexico. We reexamined the ∼4000 specimens of the type series and measured representative teeth (n = 88) for mesiodistal length, crown width, and crown height. Reticulodus exhibits moderate monognathic heterodonty. We then assigned almost all teeth to one of three morphotypes (I–III) defined by ratios of crown width to mesiodistal length, with morphotype I being the most equilateral and morphotype III the most elongate. A fourth morphotype (IV) possesses very low crown width to mesiodistal length ratios and is tentatively considered as posterolateral in position. Adult teeth measure 1–10 mm long, with apical surfaces ornamented with numerous reticulations, crenulations, and pits, and appear subrounded, rectangular, or hexagonal in apical view—these teeth probably enabled a durophagous diet. Juvenile teeth measure approximately 0.7–2 mm in length, exhibit greater variation in crown shape than do adult teeth, and possess a clutching-type dentition that would facilitate the capture and consumption of softer-bodied organisms. The dentition thus transitioned from a clutching-type in juveniles to a grinding-type in adults, which would have allowed both adults and juveniles to occupy the same habitat and suppressed intraspecific competition between the two age groups.

Second-day road log, from Gallup to Fort Wingate, Sixmile Canyon, Ciniza, Red Rock Park, Church Rock, White Mesa, Thoreau and Grants

A hypothesis: autonomic rhythms are reflected in growth lines of teeth in humans and extinct archosaurs

Autonomic Neuroscience: Basic and Clinical, Feb 1, 2005

A major determinant of tooth architecture is the arrangement of lines in dentin and in the enamel... more A major determinant of tooth architecture is the arrangement of lines in dentin and in the enamel following the contour of the surface. Since the original description of these lines in the 19th century, they have been attributed to recurring events during tooth development. They have also attracted the attention of dental scientists and anthropologists; however, to date, studies of these structures have been largely theoretical and microscopic. We show here that the statistical properties of the spacing between the lines are similar in teeth from both ancient and modern humans and from extinct archosaurs, reptiles that lived tens or hundreds of millions of years ago-they also resemble heart rate variability of living humans. We propose that the deposition of these recurring structures is controlled by the autonomic nervous system. This control accounts for their regularity and recurrent nature and implies that the lines are an expression of a biologic rhythm which has been conserved throughout evolution. Details of the rhythms give clues to life styles in ancient civilizations and to the physiology of extinct archosaurs.

The Rousseau H. Flower Invertebrate Fossil Collection: Conservation and Curation

New Mexico Geological Society Annual Spring Meeting, Apr 18, 2008

Vertebrate fauna of the late Campanian (Judithian) Fort Crittenden Formation, and the age of Cretaceous vertebrate faunas of southeastern Arizona (U.S.A.)

Neues Jahrbuch für Geologie und Paläontologie, Apr 10, 2003

Lateral Line Groove Development as a Measure of Terrestriality in Late Triassic Metoposaurid Amphibians

New Mexico Geological Society Annual Spring Meeting, Apr 24, 2009

Supplemental road log 1: From Grants to eastern margin of El Malpais, Sandstone Bluffs Overlook, and McCartys lava flow

The vertebrate fauna of the Upper Triassic (Norian: Revueltian) Snyder quarry

Since the first scientific excavations, it has been apparent that the Snyder quarry represents a ... more Since the first scientific excavations, it has been apparent that the Snyder quarry represents a unique vertebrate fossil assemblage. This assemblage includes an apparent xenacanthid shark, semionotid and redfieldiid fish, a metoposaurid amphibian, a probable procolophonid reptile, a cynodont, an apparent lepidosauromorph, abundant specimens of the phytosaur Pseudopalatus, the aetosaurs Typothorax coccinarum Cope and Desmatosuchus chamaensis Zeigler, Heckert and Lucas, the rauisuchian Postosuchus (sensu stricto), a sphenosuchian and theropod dinosaurs referable to Eucoelophysis. Archosaurs dominate the assemblage, and the phytosaurs, and aetosaurs are all treated separately elsewhere in this volume. The xenacanth apparently pertains to the "Xenacanthus" moorei group and, if it is not a contaminant from screenwashing processes, is one of the youngest xenacanth sharks known. Most osteichthyan fossils at the Snyder quarry are isolated scales and bones, though an incomplete, articulated semionotid has been recovered. The sole metoposaurid fossils recovered to date are a fragmentary, large centrum and isolated teeth that probably pertain to Buettneria and would thus be one of the youngest Buettneria records known. The possible procolophonid fossil consists of a single tooth and remains problematic. The cynodont is represented by an incomplete left distal humerus. The lepidosauromorph is based on an incomplete jaw fragment bearing many pleurodont teeth. The archosaur fauna is somewhat typical of Revueltian Chinle faunas in that it includes the phytosaur Pseudopalatus and the aetosaur Typothorax coccinarum, both index taxa of the Revueltian (early-mid Norian) land-vertebrate faunachron. Rarer archosaurian taxa include the aetosaur Desmatosuchus chamaensis, the theropod dinosaurs, the rauisuchian Postosuchus and the indeterminant sphenosuchian. The rauisuchian is represented by fragmentary postcrania that, from their disparate sizes, clearly represent at least two different individuals.

Preliminary description of coelophysoids (Dinosauria:Theropoda) from the Upper Triassic (Revueltian:early-mid Norian) Snyder quarry, north-central New Mexico

The Upper Triassic Snyder quarry is the second-most productive theropod locality in the Chinle Gr... more The Upper Triassic Snyder quarry is the second-most productive theropod locality in the Chinle Group. Skull and postcranialelements, particularly tibiae, collected from the Snyder quarry during the last three field seasons demonstrate the presence of at least four individuals of two taxa. The smaller theropod strongly resembles, but is distinct from, the holotype of Eucoelophysis baldwini Sullivan and Lucas and represents either a sexual dimorph or, more likely, a new species of Eucoelophysis. The larger theropod is represented by a single, incomplete fused tibia-fibula-astragalus-calcaneum. Most striking about this taxon is the proximal fusion of the tibia and fibula. These theropods are a small fraction of a rich and diverse assemblage of Upper Triassic vertebrates and invertebrates from the most productive Chinle Group vertebrate fossil assemblage discovered in the last 50 years.

Cretaceous dinosaurs in New Mexico

New Mexico's most extensive fossil record of dinosaurs is from rocks of Cretaceous age. The Early... more New Mexico's most extensive fossil record of dinosaurs is from rocks of Cretaceous age. The Early Cretaceous record is confined to tracks of late Albian age, principally from northeastern NM. They are primarily of ornithopods (Caririchnium, Amblydactylus) and lesser numbers of theropods. They provide circumstantial evidence of social behavior in ornithopods and, because of the lack of sauropod tracks, suggest the extirpation of North American sauropods took place during the late Albian. New Mexico's record of Late Cretaceous dinosaurs includes a few tracksites (notably including the holotype of Tyrannosauripus from the late Maastrichtian of the Raton basin) and an extensive body fossil record from rocks of late Turonian, late Santonian, Campanian and Maastrichtian age. Highlights of this record include: (1) Zuniceratops from the late Turonian Moreno Hill Formation, the oldest North American ceratopsian with brow horns, which suggests a possible North American origin of ceratopsids; (2) hadrosaur, ceratopsian and theropod fossils from the late Santonian Crevasse Canyon Formation and early Campanian Menefee Formation that are mostly fragmentary and isolated but that indicate a need to collect further this largely unsampled interval; (3) an extensive late Campanian record from the Fruitland and Kirtland formations in the San Juan Basin that provides strong evidence of Asian-North American interchange of Campanian dinosaurs; and (4) a possible Paleocene dinosaur record from the San Juan Basin.

Stratigraphy, taphonomy, and new discoveries from the Upper Jurassic (Morrison Formation: Brushy Basin Member) Peterson quarry, central New Mexico

The Upper Jurassic Peterson quarry, located in Bernalillo County, central New Mexico, is New Mexi... more The Upper Jurassic Peterson quarry, located in Bernalillo County, central New Mexico, is New Mexico's most extensive and productive Jurassic dinosaur locality. The quarry is developed in the upper Brushy Basin Member of the Morrison Formation, approximately 26 m below its contact with the overlying Jackpile Member. Bones occur low in a 3.3-m-thick sequence of well-indurated, troughcrossbedded, subarkosic sandstone. Preserved elements range from scattered bones to articulated assemblages of bones from a single individual, and the long bones are preferentially oriented along a generally east-west-trending axis. The occurrence of associated-to-articulated bones in a troughcrossbedded sandstone underlying a floodplain mudstone suggests deposition of the fossils in the mixed fill of an abandoned channel in a typical Brushy Basin Member fluvial system. Particularly important dinosaurs from the Peterson quarry include a large (1100 mm estimated. femoral length) Saurophaganax-like allosaurid theropod and the anterior portion of a diplodocid skull and lower jaws similar to Diplodocus. This specimen is one of less than a dozen Morrison Formation diplodocid skulls known and is particularly important because it is: (1) the only Jurassic sauropod skull material from New Mexico; (2) could represent a genus and/or species of Morrison diplodocid from which skull material is not yet known; and (3) provides insight into the replacement pattern of diplodocid teeth. FIGURE 3. Photographs of the Peterson quarry. A, Overview of the quarry on 18 July 1999. The principal bonebed is the arroyo bottom partially filled with water. B, View in the quarry on 2 July 1995 showing trough-crossbedded, channelform sandstone geometry of bone-bearing sandstone interval; man on left is covering a pedestaled bone. C, Sauropod tibia and fibula in the quarry, 16 May 1999. D, Articulated theropod bones in the quarry, 22

A Revueltian (Norian) phytosaur from the Sonsela Member of the Petrified Forest Formation (Chinle Group: Upper Triassic), Petrified Forest National Park, Arizona

The Sonsela Member of the Petrified Forest Formation (Upper Triassic) is widely exposed in northe... more The Sonsela Member of the Petrified Forest Formation (Upper Triassic) is widely exposed in northeastern Arizona and northwestern New Mexico. Fossil wood is common in the fluvial Sonsela, but the high energy depositional conditions appear to have destroyed all fossil bone except for small fragments. The first identifiable vertebrate fossil from channel-facies of this unit is an incomplete phytosaur skull preserved on a fallen block of sandstone on a cliff in the Rainbow Forest area of Petrified Forest National Park, Arizona. This cliff is "Flattops Sandstone I," which we consider to represent the upper part of the Sonsela Member. The left side of the skull, lacking the anterior half of the rostrum, is preserved in lateral view. The specimen is uncollectable, but casts are preserved at Mesalands Dinosaur Museum, Petrified Forest National Park, and the New Mexico Museum of Natural History and Science. The two most important morphological features of this specimen are: (1) the external nares are at approximately the same level as the skull deck; and (2) the posterior squamosal process in lateral view is narrow and not pendulous. This combination of features is diagnostic of the genus Nicrosaurus. The only other published account of Nicrosaurus in North America is Nicrosaurus buceros from the Chama basin of north-central New Mexico. The common Nicrosaurus kapffi and the rare N. meyeri occur in the Norian Stubensandstein of southwestern Germany. This specimen is biochronologically sig:p.ificant as it demonstrates that the Sonsela is indeed Norian in age, as has been suggested previously. Paleobiogeographically, it is one of an increasing number of Late Triassic tetrapod taxa that were previously thought to be exclusively European in distribution (e.g., Erpetosuchus, Aetosaurus, Stagonolepis) that have now been identified in North America.

The microvertebrate fauna of the Upper Triassic (Revueltian) Snyder Quarry, north-central New Mexico

The Snyder quarry is a well-documented assemblage of Late Triassic invertebrates and vertebrates ... more The Snyder quarry is a well-documented assemblage of Late Triassic invertebrates and vertebrates from the Painted Desert Member of the Upper Triassic Petrified Forest Formation in the Chama Basin, north-central New Mexico. The presence of Revueltian index taxa, including the aetosaurs Typothorax coccinarum and Desmatosuchus chamaensis and the phytosaur Pseudopalatus buceros, demonstrate that the Snyder quarry is of Revueltian (early-mid Norian) age. Screenwashing matrix from the primary bonebed at the Snyder quarry yielded a moderately diverse assemblage of microvertebrates, some of which were not represented in the macrovertebrate fauna. Microvertebrate fossils from the Snyder quarry are mostly scales and bone fragments-complete teeth are unusually rare. New records include a tooth of the hybodontoid shark Lonchidion and numerous scales of a palaeoniscid fish tentatively assigned to aff. Turseodus. The microvertebrate assemblage differs somewhat from the known macrovertebrate assemblage, and includes many more osteichthyan fossils. Osteichthyans dominate the microvertebrate fauna, and include semionotids, redfieldiids, palaeoniscoids, and indeterminate sarcopterygians. Osteichthyans are largely represented by scales, with the exception of the indeterminate sarcopterygians and actinopterygians, represented by fragments of dentigerous toothplates, fossils previously assigned to "colobodontids." The microvertebrate tetrapod fauna represented by teeth includes metoposaurid amphibians, juvenile (?) phytosaurs (?), probable dinosaurs, aetosaurs and other diverse, unidentified archosauromorphs. Many of the vertebrae appear to pertain to small archosauromorphs. The microvertebrate assemblage is unusual in that recovered vertebrae and other non-cranial elements greatly outnumber intact teeth, which normally dominate Chinle microvertebrate assemblages. We interpret this as additional support for the hypothesis of a catastrophic origin for the Snyder quarry vertebrate assemblage, as more typical Chinle Group microvertebrate assemblages are attritional deposits in which teeth greatly outnumber vertebrae.

Triassic Dinosaurs in New Mexico

New Mexico has a sparse but growing record of Jurassic dinosaurs. The oldest records are theropod... more New Mexico has a sparse but growing record of Jurassic dinosaurs. The oldest records are theropod footprints and a sauropod vertebra from the Middle-Upper Jurassic Summerville Formation. The footprints are part of a widespread large theropod-pterosaur ichnofacies in the Summerville and equivalent strata in the southern Western Interior. The sauropod is one of the oldest North American sauropods. The oldest theropod eggshell is from the Upper Jurassic Morrison Formation in New Mexico. Most New Mexican Jurassic dinosaurs are from the Upper Jurassic Morrison Formation and include Apatosaurus, Diplodocus carnegiei, Diplodocus (=Seismosaurus) hallorum, Camarasaurus, Allosaurus, and Stegosaurus. These dinosaurs are part of a homogenous Morrison dinosaur chronofauna found throughout the Western Interior and characteristic of the Comobluffian land-vertebrate faunachron.

A new dinosaur footprint locality from the Dakota Sandstone (Upper Cretaceous: Cenomanian) in west-central New Mexico

We assign two incomplete dinosaur tracks from the Dakota Sandstone in Socorro County, west-centra... more We assign two incomplete dinosaur tracks from the Dakota Sandstone in Socorro County, west-central New Mexico to the ichnogenus Caririchnium sp., widely believed to represent the tracks of an iguanodontid ornithopod dinosaur. This is the first record of Cretaceous dinosaur tracks from west of the Rio Grande rift in New Mexico. Previous work suggests that the Dakota Sandstone in west-central New Mexico is of middle Cenomanian age, which makes these tracks younger than those of the so-called "dinosaur freeway" in the Dakota Group of northeastern New Mexico and eastern Colorado.

The tetrapod fauna of the Upper Triassic lower Chinle Group (Adamanian:latest Carnian), of the Zuni Mountains, west-central New Mexico

Numerous localities in the Bluewater Creek Formation in the Zuni Mountains of westcentral New Mex... more Numerous localities in the Bluewater Creek Formation in the Zuni Mountains of westcentral New Mexico produce a tetrapod fauna that includes the metoposaurid amphibian Buettnena sp., indeterminate phytosaurs, the aetosaurs Stagonolepis, Desmatosuchus, and Paratypothorax, two theropod dinosaurs, at least two ornithischian dinosaurs, including one identified here as aff. Tecovasaunls, and trace fossils consisting of a footprint of an ?ornithischian, and vertebrate coprolites. The most frequently encountered fossils are abundant cranial and postcranial fragments of metoposaurid amphibians and indeterminate phytosaurs. Stagonolepis is an index taxon of the Adamanian land-vertebrate faunachron, indicating that the Bluewater Creek Formation is latest Carnian in age, an observation consistent with abundant Desmatosuchus and large metoposaurid amphibians. The overlying Blue Mesa Member of the Petrified Forest Formation is relatively unfossiliferous in the Zuni Mountains, and has only produced fragmentary remains of indeterminate metoposaurs and phytosaurs, but produces an Adamanian fauna from various localities in Arizona. The dinosaur fauna from the Bluewater Creek Formation comes from a single locality, is the most diverse late Carnian dinosaur assemblage in North America, and includes some of the oldest known dinosaurs.

THE LATE TRIASSIC ARCHOSAUROMORPH <em>TRILOPHOSAURUS </em> AS AN ARBOREAL CLIMBER

DOAJ (DOAJ: Directory of Open Access Journals), Nov 1, 2005

Two species of the unusual archosauromorph Trilophosaurus, T. buettneri Case and T. jacobsi Murry... more Two species of the unusual archosauromorph Trilophosaurus, T. buettneri Case and T. jacobsi Murry, are known from diverse localities in the Upper Triassic Chinle Group in the southwestern USA. Both species likely occupied similar ecological niches, based on morphological similarities in the postcrania, which are essentially identical. Trilophosaurus occurrences in the Chinle Group are relatively rare, but individual sites are exceptionally rich, suggesting that Trilophosaurus lived in a different paleoenvironment than more typical Chinle vertebrates, which lived in or near streams (phytosaurs, metoposaurs) or on floodplains (aetosaurs, rauisuchians, and dinosaurs). Two potential interpretations are that Trilophosaurus was either an arboreal climber or a fossorial digger. However, the gross skeletal features of Trilophosaurus are not compatible with a fossorial mode of life: the limbs are too long and gracile, proximal limb elements are longer than distal ones, and the claws are laterally compressed, not transversely broadened. The intermittent study of Trilophosaurus has caused the theory of it being arboreal, originally proposed by Gregory, to receive little mention in subsequent studies. We reexamined the functional morphology of Trilophosaurus using a qualitative functional morphological analysis of the skeleton, a quantitative examination of claw curvature, and a quantitative examination of manus/trunk and pes/ trunk ratios. Claw morphology of Trilophosaurus shows similarities to the arboreal drepanosaurs Drepanosaurus and Megalancosaurus. Our analysis provides ample evidence to suggest that Trilophosaurus was arboreal. Riassunto. Nel Gruppo Chinle (Triassico Superiore) del Sudovest degli USA sono note due specie dell'insolito arcosauromorfo Trilophosaurus, T. buettneri Case e T. jacobsi Murry, provenienti da diverse localita Á . Probabilmente entrambe le specie occupavano nicchie ecologiche simili, sulla base di affinita Á morfologiche nelle ossa postcraniche, che sono sostanzialmente identiche. I ritrovamenti di Trilophosaurus nel Gruppo Chinle sono relativamente rari, ma singole localita Á possono essere significativamente ricche, suggerendo che Trilophosaurus vivesse in un ambiente diverso da quello dei tipici vertebrati della Chinle, che popolavano i fiumi o le loro vicinanze (fitosauri, metoposauri) o le piane alluvionali (aetosauri, rauisuchii e dinosauri). Due interpretazioni etologiche sono possibili, e cioe Á che Trilophosaurus fosse un arboricolo, oppure uno scavatore. Tuttavia le caratteristiche scheletriche principali di Trilophosaurus non sono compatibili con lo stile di vita di un fossatore: le zampe sono troppo lunghe e gracili, gli elementi prossimali delle zampe sono piu Á lunghi di quelli distali, e gli artigli sono compressi lateralmente e non allargati in senso trasversale. Essendo sporadici gli studi su Trilophosaurus l'interpretazione che fosse arboricolo, proposta inizialmente da Gregory, ricevette poca attenzione negli studi successivi. Noi abbiamo riesaminato la morfologia funzionale di Trilophosaurus utilizzando l'analisi qualitativa della morfologia funzionale dello scheletro, la valutazione quantitativa della curvatura degli artigli, e dei rapporti manus/tronco e pes/tronco. La morfologia degli artigli di Trilophosaurus mostra somiglianze con i drepanosauri arboricoli Drepanosaurus and Megalancosaurus. La nostra analisi fornisce ampie evidenze per sostenere che Trilophosaurus fosse arboricolo.

The microfauna of the Upper Triassic Ojo Huelos Member, San Pedro Arroyo Formation, central New Mexico, U.S.A

Three fossiliferous horizons at the type section of the Upper Triassic Ojo Huelos Member of the S... more Three fossiliferous horizons at the type section of the Upper Triassic Ojo Huelos Member of the San Pedro Arroyo Formation yield a microfauna of ostracodes, "spirorbids," sharks, bony fish, and tetrapods. These fossils represent a rare lacustrine microfossil assemblage near the base of the Upper Triassic Chinle Group. The fossiliferous interval consists primarily of pisolitic limestone and sandy mudstone. The fauna includes the ostracodes Darwinula sp., and Gerdalia sp., "spirorbid polychaetes," the hybodont shark Lissodus humblei, several morphotypes of actinopterygian fish, including redfieldiids and semionotids, fragmentary labyrinthodont amphibians, and indeterminate reptiles. Darwinula is the most common fossil. Numerically, Lissodus, known from dozens of teeth, dominates the vertebrate fauna, followed by actinopterygians. The smallest teeth of Lissodus from this locality are the smallest teeth known for the genus. This assemblage is consistent with an early Late Triassic (Carnian) age, and lithostratigraphic position suggests that this fauna is probably of Adamanian (latest Carnian) age. Carbonates of definitive lacustrine origin are rare in the Chinle, and this fauna documents the first discovery of microvertebrate tetrapods in lacustrine limestones of the Chinle Group. Because this microvertebrate fauna is clearly from an aquatic environment, this favors an aquatic (not scatologic) origin for similar fish-dominated microvertebrate faunas in the Chinle.

The Paleobiology of Coelophysis bauri (Cope) from the Upper Triassic (Apachean) Whitaker quarry, New Mexico, with detailed analysis

A new aetosaur (Archosauria: Pseudosuchia) from the upper Blue Mesa Member (Adamanian: Early–Mid Norian) of the Late Triassic Chinle Formation, northern Arizona, USA, and a review of the paratypothoracin <i>Tecovasuchus</i> across the southwestern USA

PaleoBios, Jul 17, 2023

Cover: Stratigraphic (A) and geographic occurrences (B) of the new typothoracine Kryphioparma cae... more

Ontogenetic heterodonty in<i>Reticulodus synergus</i>(Chondrichthyes, Hybodontiformes) from the Upper Triassic of the southwestern U.S.A., with a redescription of the genus

Journal of Vertebrate Paleontology, Jul 4, 2017

ABSTRACT Isolated teeth from the extinct hybodontoid Reticulodus synergus Murry and Kirby are kno... more ABSTRACT Isolated teeth from the extinct hybodontoid Reticulodus synergus Murry and Kirby are known from Upper Triassic strata of Revueltian age in Arizona, Utah, and New Mexico, U.S.A. Here, we provide evidence for ontogenetic heterodonty in Reticulodus based on a reappraisal of the type and newly discovered material from the Upper Triassic Bull Canyon Formation in east-central New Mexico. We reexamined the ∼4000 specimens of the type series and measured representative teeth (n = 88) for mesiodistal length, crown width, and crown height. Reticulodus exhibits moderate monognathic heterodonty. We then assigned almost all teeth to one of three morphotypes (I–III) defined by ratios of crown width to mesiodistal length, with morphotype I being the most equilateral and morphotype III the most elongate. A fourth morphotype (IV) possesses very low crown width to mesiodistal length ratios and is tentatively considered as posterolateral in position. Adult teeth measure 1–10 mm long, with apical surfaces ornamented with numerous reticulations, crenulations, and pits, and appear subrounded, rectangular, or hexagonal in apical view—these teeth probably enabled a durophagous diet. Juvenile teeth measure approximately 0.7–2 mm in length, exhibit greater variation in crown shape than do adult teeth, and possess a clutching-type dentition that would facilitate the capture and consumption of softer-bodied organisms. The dentition thus transitioned from a clutching-type in juveniles to a grinding-type in adults, which would have allowed both adults and juveniles to occupy the same habitat and suppressed intraspecific competition between the two age groups.

Second-day road log, from Gallup to Fort Wingate, Sixmile Canyon, Ciniza, Red Rock Park, Church Rock, White Mesa, Thoreau and Grants

A hypothesis: autonomic rhythms are reflected in growth lines of teeth in humans and extinct archosaurs

Autonomic Neuroscience: Basic and Clinical, Feb 1, 2005

A major determinant of tooth architecture is the arrangement of lines in dentin and in the enamel... more A major determinant of tooth architecture is the arrangement of lines in dentin and in the enamel following the contour of the surface. Since the original description of these lines in the 19th century, they have been attributed to recurring events during tooth development. They have also attracted the attention of dental scientists and anthropologists; however, to date, studies of these structures have been largely theoretical and microscopic. We show here that the statistical properties of the spacing between the lines are similar in teeth from both ancient and modern humans and from extinct archosaurs, reptiles that lived tens or hundreds of millions of years ago-they also resemble heart rate variability of living humans. We propose that the deposition of these recurring structures is controlled by the autonomic nervous system. This control accounts for their regularity and recurrent nature and implies that the lines are an expression of a biologic rhythm which has been conserved throughout evolution. Details of the rhythms give clues to life styles in ancient civilizations and to the physiology of extinct archosaurs.

The Rousseau H. Flower Invertebrate Fossil Collection: Conservation and Curation

New Mexico Geological Society Annual Spring Meeting, Apr 18, 2008

Vertebrate fauna of the late Campanian (Judithian) Fort Crittenden Formation, and the age of Cretaceous vertebrate faunas of southeastern Arizona (U.S.A.)

Neues Jahrbuch für Geologie und Paläontologie, Apr 10, 2003

Lateral Line Groove Development as a Measure of Terrestriality in Late Triassic Metoposaurid Amphibians

New Mexico Geological Society Annual Spring Meeting, Apr 24, 2009

Supplemental road log 1: From Grants to eastern margin of El Malpais, Sandstone Bluffs Overlook, and McCartys lava flow

The vertebrate fauna of the Upper Triassic (Norian: Revueltian) Snyder quarry

Since the first scientific excavations, it has been apparent that the Snyder quarry represents a ... more Since the first scientific excavations, it has been apparent that the Snyder quarry represents a unique vertebrate fossil assemblage. This assemblage includes an apparent xenacanthid shark, semionotid and redfieldiid fish, a metoposaurid amphibian, a probable procolophonid reptile, a cynodont, an apparent lepidosauromorph, abundant specimens of the phytosaur Pseudopalatus, the aetosaurs Typothorax coccinarum Cope and Desmatosuchus chamaensis Zeigler, Heckert and Lucas, the rauisuchian Postosuchus (sensu stricto), a sphenosuchian and theropod dinosaurs referable to Eucoelophysis. Archosaurs dominate the assemblage, and the phytosaurs, and aetosaurs are all treated separately elsewhere in this volume. The xenacanth apparently pertains to the "Xenacanthus" moorei group and, if it is not a contaminant from screenwashing processes, is one of the youngest xenacanth sharks known. Most osteichthyan fossils at the Snyder quarry are isolated scales and bones, though an incomplete, articulated semionotid has been recovered. The sole metoposaurid fossils recovered to date are a fragmentary, large centrum and isolated teeth that probably pertain to Buettneria and would thus be one of the youngest Buettneria records known. The possible procolophonid fossil consists of a single tooth and remains problematic. The cynodont is represented by an incomplete left distal humerus. The lepidosauromorph is based on an incomplete jaw fragment bearing many pleurodont teeth. The archosaur fauna is somewhat typical of Revueltian Chinle faunas in that it includes the phytosaur Pseudopalatus and the aetosaur Typothorax coccinarum, both index taxa of the Revueltian (early-mid Norian) land-vertebrate faunachron. Rarer archosaurian taxa include the aetosaur Desmatosuchus chamaensis, the theropod dinosaurs, the rauisuchian Postosuchus and the indeterminant sphenosuchian. The rauisuchian is represented by fragmentary postcrania that, from their disparate sizes, clearly represent at least two different individuals.

Preliminary description of coelophysoids (Dinosauria:Theropoda) from the Upper Triassic (Revueltian:early-mid Norian) Snyder quarry, north-central New Mexico

The Upper Triassic Snyder quarry is the second-most productive theropod locality in the Chinle Gr... more The Upper Triassic Snyder quarry is the second-most productive theropod locality in the Chinle Group. Skull and postcranialelements, particularly tibiae, collected from the Snyder quarry during the last three field seasons demonstrate the presence of at least four individuals of two taxa. The smaller theropod strongly resembles, but is distinct from, the holotype of Eucoelophysis baldwini Sullivan and Lucas and represents either a sexual dimorph or, more likely, a new species of Eucoelophysis. The larger theropod is represented by a single, incomplete fused tibia-fibula-astragalus-calcaneum. Most striking about this taxon is the proximal fusion of the tibia and fibula. These theropods are a small fraction of a rich and diverse assemblage of Upper Triassic vertebrates and invertebrates from the most productive Chinle Group vertebrate fossil assemblage discovered in the last 50 years.