PBDB Collection

Mygatt-Moore Quarry, lower mudstone (Jurassic to of the United States)

Also known as MWC Loc. 1.05.86, MWC Loc. 2, CO-21, main quarry, MMQ

Where: Mesa County, Colorado (39.2° N, 109.0° W: paleocoordinates 35.3° N, 55.6° W)

• coordinate estimated from map

• outcrop-level geographic resolution

When: Brushy Basin Member (Morrison Formation), Kimmeridgian to Kimmeridgian (157.3 - 145.0 Ma)

• middle part of member

•

•Ash fall zircons from the site were U-Pb dated to 152.3 +/- 0.2Ma placing the site near the Kimmeridgian–Tithonian boundary (Trujillo et al. 2014)

• group of beds-level stratigraphic resolution

Environment/lithology: pond; lithified, gray, green, silty, conglomeratic mudstone and lithified, pebbly, calcareous conglomerate

• The fossil-bearing unit is about 2m thick and consists of green-grey silty mudstone and conglomerate. Most of the bones lie at the bottom of this unit, whereas the fossil plants are distributed throughout the bed. This unit is underlain by beds of red, purple, and green-hued carbonate, mudstone, fine sandstone, and siltstone. The base of the fossil-bearing unit is incised into the underlying carbonate unit, or even into the oxidized, muddy siltstone beneath the carbonate unit. Bones are often incorporated within lenses of conglomerate consisting of subrounded to rounded carbonate pebbles. Kirkland and Carpenter (1994) interpreted the carbonate pebbles to be transported calcareous soil nodules, but they may be rip-up clasts from the carbonate unit that underlies the fossil bearing unit in some areas.

• The fossiliferous unit is overlain by a bed of resistant, fine-grained volcanic tuff which is well cemented and tends to break perpendicular to the bedding. It was from this tuff that one nearly complete articulated fish, and parts of several others, were recovered (see Kirkland, this volume).

•The presence of a laterally continuous carbonate bed below the quarry, and two laterally continuous tuff units above, indicates that the tuffs were deposited in a predominantly lacustrine environment. Based on the lateral extent of the tuffs, it is estimated that the lake was at least 1.5 km wide. The occurrence of articulated fish in the lower tuff unit indicates deposition in quiet water, although the presence of ripple marks suggest that the water was relatively shallow at times. The fact that fossil root casts are present in the tuff to the southwest and east of Rabbit Valley, but absent in the area of the quarry, implies that the lake level receded temporarily, although water remained in the area of the quarry. The disconformable base of the fossiliferous unit which contains lenses of carbonate pebbles and bone, suggests evidence for temporary fluvial conditions when the unit was first being deposited.

Size classes: macrofossils, microfossils

Preservation: cast, adpression, trace, soft parts, permineralized, original carbon, original sporopollenin, replaced with silica

Collected by J. Moore, V. Moore, P. Mygatt, M. Mygatt in 1981, 1985–

Collection methods: quarrying, mechanical, peel or thin section, sieve,

• discovered on March 14, 1981, by J.D. and Vanetta Moore and Pete and Marilyn Mygatt

Primary reference: J. I. Kirkland and H. J. Armstrong. 1992. Taphonomy of the Mygatt-Moore (M&M) Quarry, middle Brushy Basin Member, Morrison Formation (Upper Jurassic) western Colorado. Journal of Vertebrate Paleontology 12(3, suppl.):55A [A. Behrensmeyer/A. Behrensmeyer/J. Alroy]more details

Purpose of describing collection: taxonomic analysis

PaleoDB collection 11611: authorized by Kevin Boyce, entered by Kevin Boyce on 24.08.2001, edited by Matthew Carrano

Creative Commons license: CC BY (attribution)

Taxonomic list

Show authors, comments, and common names

unclassified
-	Steinerocaulis radiatus¹⁰ Steinerocaulis radiatus¹⁰ casts and impressions
Amphibia
Caudata -	Caudata indet.⁵ Caudata indet.⁵ Scopoli 1777 salamander MWC 8649, limb bone
Reptilia
-	Reptilia indet.⁵ Reptilia indet.⁵ Laurenti 1768 reptile conical tooth
Archosauria -	Archosauria indet.⁵ Archosauria indet.⁵ Cope 1869 archosaur vertebral centrum (either ornithopod or goniopholidid); limb bone (theropod or pterosaur)
Dinosauria -	Dinosauria indet.⁴ Dinosauria indet.⁴ Owen 1842 dinosaur MWC 1903
Ornithischia - Nodosauridae	Mymoorapelta maysi n. gen. n. sp.⁸ Mymoorapelta maysi n. gen. n. sp.⁸ Kirkland and Carpenter 1994 ankylosaur 17 specimens
Ornithischia -	"Othnielosaurus consors" = Nanosaurus agilis⁶ "Othnielosaurus consors" = Nanosaurus agilis⁶ Marsh 1877 ornithopod MWC 5966, jaw fragment
Theropoda -	Theropoda indet.⁸, Ceratosaurus nasicornis⁵, Allosaurus fragilis² Theropoda indet.⁸ theropod Ceratosaurus nasicornis⁵ Marsh 1884 ceratosaur shed teeth Allosaurus fragilis² Marsh 1877 allosauroid
Saurischia -	Sauropoda indet.³, ? Sauropoda indet.⁴ Sauropoda indet.³ Marsh 1878 sauropod MWC 1916, 1917, 3828, 3769, 3738 ? Sauropoda indet.⁴ Marsh 1878 sauropod MWC 6718, 5537
Saurischia - Camarasauridae	Camarasaurus cf. lentus⁵, Camarasaurus cf. lentus⁵ Camarasaurus cf. lentus⁵ Marsh 1889 camarasaurid MWC 5051, 5009 Camarasaurus cf. lentus⁵ Marsh 1889 camarasaurid MWC 2538
Saurischia - Diplodocidae	Apatosaurus cf. louisae⁵, Diplodocinae indet.⁶, Diplodocinae indet.⁶ Apatosaurus cf. louisae⁵ Holland 1915 diplodocid MWC 1848, 5072 Diplodocinae indet.⁶ diplodocine Diplodocinae indet.⁶ diplodocine caudal vertebrae
Pterosauria -	Pterosauria indet.⁷ Pterosauria indet.⁷ pterosaur MWC 5728, hollow limb element
Loricata - Goniopholididae	Goniopholididae indet.⁶ Goniopholididae indet.⁶ Cope 1875 crocodilian MWC 1902, vertebra; tooth
Lepidosauria -	Rhynchocephalia indet.⁵ Rhynchocephalia indet.⁵ Günther 1867 rhynchocephalian MWC 8671, R dentary
Eosuchia -	cf. Opisthias sp.⁸ cf. Opisthias sp.⁸ Gilmore 1909 lepidosaur
Testudines -	"Chelonia indet." = Testudines⁹ "Chelonia indet." = Testudines⁹ Batsch 1788 turtle
Actinopteri
Semionotiformes - Semionotidae	Semionotidae indet.⁸ Semionotidae indet.⁸ Woodward 1890
Gastropoda
Architaenioglossa - Viviparidae	Viviparus reesidei⁵ Viviparus reesidei⁵ snail
Cycadeoideopsida
Cycadeoideales -	Conites sp.⁵ Conites sp.⁵ Sternberg 1823 seed cones
Hermanophyton
-	Hermanophyton sp.⁸ Hermanophyton sp.⁸ Arnold 1962
Equisetopsida
Pinidae - Pinidae	Brachyphyllum rechtenii n. sp.¹⁰, Brachyphyllum "sp. A"¹⁰, Pagiophyllum sp.⁵ Brachyphyllum rechtenii n. sp.¹⁰ axis and attached leaves Brachyphyllum "sp. A"¹⁰ Brongniart 1828 Pagiophyllum sp.⁵ Heer 1881
Sphenopteridae
- Sphenopteridae	? Sphenopteris cf. metzgeriodes⁵ ? Sphenopteris cf. metzgeriodes⁵
unclassified
-	Cycadophyta indet.¹ Cycadophyta indet.¹ Bessey 1907 laminae in coprolites
Jensensispermum
-	Jensensispermum redmondii¹⁰ Jensensispermum redmondii¹⁰ seeds
Cycadopsida
Cycadales -	Behuninia provoensis¹⁰ Behuninia provoensis¹⁰ cycads cast
Ginkgoopsida
Ginkgoales - Ginkgoaceae	? Ginkgo sp.⁵ ? Ginkgo sp.⁵ Linnaeus 1771 ginkgo
Czekanowskiales -	Czekanowskia ? turneri¹⁰ Czekanowskia ? turneri¹⁰

Bennettitales - Bennettitaceae	cf. Cycadeoidea indet.¹ cf. Cycadeoidea indet.¹ Buckland 1828 petioles in coprolites
Bennettitales -	Otozamites sp.⁵, ? Cycadolepis sp.⁵ Otozamites sp.⁵ Braun 1843 ? Cycadolepis sp.⁵ Saporta 1875
Coniferales - Cupressaceae	Protocupressinoxylon medlynii n. sp.¹⁰ Protocupressinoxylon medlynii n. sp.¹⁰ cypress
Coniferales - Podocarpaceae	Mesembrioxylon carterii n. sp.¹⁰ Mesembrioxylon carterii n. sp.¹⁰ podocarp
Pinopsida
Pinales -	Xenoxylon moorei n. sp.¹⁰ Xenoxylon moorei n. sp.¹⁰ description largely based on third specimen from another locality
Lycopodiopsida
Isoetales - Isoetaceae	Isoetaceae indet.⁵ Isoetaceae indet.⁵ Dumortier 1829 clubmoss
Polypodiopsida
Cyatheales - Polypodiidae	Coniopteris sp.⁵ Coniopteris sp.⁵ Brongniart 1849 scaly tree fern
Equisetales - Equisetidae	Equisetum cf. burchardtii¹⁰, Equisetum cf. laterale⁵ Equisetum cf. burchardtii¹⁰ horsetail rhizome and tubers Equisetum cf. laterale⁵ horsetail

¹Chin and Kirkland 1998; ²Foster 2005; ³Foster 2005; ⁴Foster and Hunt-Foster 2011; ⁵Foster et al. 2018; ⁶Foster et al. 2016; ⁷King et al. 2005; ⁸Kirkland and Carpenter 1994; ⁹Mygatt 1991; ¹⁰Tidwell et al. 1998