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Triassic Coprolite Survey
I welcome comment and further discussion, either privately or through the
DML. I regret not being able to include the accompanying diagrams. BTW, with
respect to an earlier post on sauropod esophageal dead space, due to an
error in the equation for the surface area of a circle, the calculated dead
space is twice that reported, making the volume of the esophagus about 3-4
times the volume of the lungs.
- Mike Milbocker
Triassic Coprolite Survey of the Chinle Formation in the Bull Canyon Region
All measurements in inches. ?In.? specifies feature is indicated on specimen
with an arrow.
Purpose
New Mexican coprolites have been investigated by Ash (1978) and Webber and
Lawler (1978). No study has described Triassic New Mexican coprolites
containing identifiable animal remains. Coprolites with bone inclusions are
a minority of most coprolites found in this region and stratigraphy, though
Thulborn (1991) suggests that coprolites preserved in wet environments are
likely the products of carnivores or omnivores due to bone?s conversion to
apatite, a mineral that enhances preservation. The specimens of this survey
are unique in that the evidence of carnivory is direct and evidence of
herbivory is absent. This is a preliminary description of 109 Triassic
carnivore coprolites identified from approximately 3000 specimens without
surface animal-derived inclusions.
Methods
No specimens were altered, other than light cleaning, in this study. This
qualitative and quantitative analysis consists of observations of surface
features. Size was assessed by determining mean dimensions on three
orthogonal axes, and their product was checked against volumetric
displacement in water. Coprolite shape was described as either oval
(ellipsoidal), cylindrical, teardrop or taking on the shape of a large bone
inclusion. Sphincter sufficiency was described as either pinched (strong),
tapered (weak), or fractured (no sphincter effect, gravitational or
frictional separation). A variety of discrete surface features are
described that fall into broad categories, including trace impressions in
the coprolite of other organisms. A variety of inclusions are described.
Identifying Characters
Gastralia - gray ribbon-like bony material that are tapered at the ends,
tend to have fibrous structure, are flush with a break surface, appear to be
translucent, are curved, and are frequently found in the interiors of liquid
type coprolites
Liquid Type - coprolites that show influence from gravity, especially
teardrop, tend to have smooth surfaces, and are sometimes fractured or
distorted after excretion
Fish Ribs - elongate bony material, sometimes hallow, usually curved but not
tapered at the ends with round cross section, rises above the surface of the
coprolite, whitish and usually the color of associated scales.
Scales - multiple examples of similar size and shape without sharp ends
showing internal structure reflective of perimeter shape
Whole Bone - usually dominates shape of coprolite, ends display laminar
concentric rings, rare cases show vascular traces on surface, articulation
geometry, and porosity, when bone is specified as a shape the bone
determines the shape of the coprolite
Paired Impressions - Common feature on Triassic coprolites featuring paired
peg-like impressions with common inter-distance and diameter at several
locations on the coprolite surface, the placement and effect of the
impressions suggests post-excretion origin
Bubbles - Round impressions, usually shallow, of varying sizes, usually
exhibiting on one side, that side is generally the side with liquid
solidification, origin possibly due to gases or particulate
Z-line - Pattern created on bone or coprolite surface when fractures created
when substrate is impacted by blade-like teeth run perpendicular to the
blade impressions, connecting adjacent impressions, usually accompanied with
loss of material such that a zigzag channel is formed in the substrate
Tubular - a shape specification (cylindrical) wherein the orthogonal
dimensions about the centroid are not different by more than 100% and the
cross sectional area of the specimen does not vary by more than 20%.
Teardrop - a shape specification wherein the orthogonal cross sectional area
about the centroid of the specimen at one end is more than 140% of the cross
sectional area at the other end.
Oval - a shape specification wherein the orthogonal dimensions about the
centroid are different by more than 100% and the cross sectional area of the
specimen does not vary by more than 20%.
Dimple - a recessed portion on one end of the coprolite aligned with the
coprolite centroid.
Nipple - a raised portion on the end of the coprolite aligned with the
coprolite centroid.
Sphincter Sufficiency - N, pinched coprolite shaping on both ends; PF,
fractured on proximal end; DF, fractured on distal end; D, poorly shaped or
tapered on distal end; P, poorly shaped on proximal end; the distal end is
the largest cross section unless other features indicate otherwise.
Stratigraphy
The present specimens were collected from a single Chinle Formation exposure
in the Bull Canyon Formation, San Miguel County, and New Mexico. Exposures
of the Chinle Formation in New Mexico are highly productive localities for
insights into the paleoenvironments of primitive North American theropods.
The abundance and diversity of bone, teeth, and coprolite suggests the
preservational conditions resulted in a time-averaged assemblage of
contemporaneous organisms. The highest concentration of coprolites is
preserved in characteristic iron and aluminum depleted blue paleosol
horizons. The blue color is indicative of redoximorphic paleosols associated
with floodplains that have undergone significant fluctuations in water
saturation.
The Late Triassic Chinle Formation consists of fluvial deposits on the
western margin of Pangea. Paleomagnetic data places the Chinle basin between
5o and 15o north of the Late Triassic paleoequator. Purple and red colors
found in the paleosol indicates drained, oxidative conditions where there is
particular abundance of iron oxides. The greenish and bluish colors observed
indicate iron depletion related to water saturation and reductive
conditions.
The paleosol sequence from which the present specimens are derived are
depleted in Fe and Mn, but rich in Fe-Mn mottles. These concentrations are
formed during times of high but fluctuating water tables with poor drainage.
To obtain the right reducing conditions, it is likely the soil was saturate
25-50% of the year (Daniels et al, 1971). The reduction of FE and MN forms
FE and MN concentrations when there exists alternating oxidative and
reductive conditions.
The blue-colored paleosol is unique to the stratigraphy and was deposited
over a channel filled with crevasse-splay deposits. Carbonate nodules are
notably absent in the blue layer. The crevasse deposits are comprised of
mudstone and siltstone intervals in the center of the channel. The blue
paleosol is comprised of a top mudstone layer in which most of the preserved
material was found. The Zr content of the blue horizon is uniform throughout
its layers, and different from the surrounding red layers. The red layers
are also characteristically higher in Al, Fe, and Mn content, and the Fe-Mn
mottles are absent. This suggests the bone-bearing layer was developed from
a source other than the underlying layer, possibly as a result of several
depositional episodes resulting in significantly varying oxidative and
reductive conditions.
Preservation conditions were optimal during a time of semi-arid climate with
strong seasonality of precipitation and flooding. The site is principally a
floodplain comprised of meandering rivers. It is unknown whether the
preserved remains map out the location of organism interaction or whether
these materials were aggregated by the changing environmental conditions.
The blue paleosol is uniquely rich in plant root remains suggesting
herbaceous and arborescent colonization near water, which may be
coincidental with faunal gatherings.
Other Fauna Evidence
The fauna was comprised principally of aetosaurs, rauisuchians,
ornithichians, pterosaurs, prosauropods, phytosaurs and metoposaurs. The
preponderance of type-specific evidence is comprised of teeth, claws, and
vertebral bodies found at the site. The site preserved many bone fragments,
but these were not attributable to any particular fauna type, except that
most are long bone-derived with a radius of about 2 cm, many of which show
regularly spaced blade-like and conical teeth traces on the margins.
Teeth remains were found that resemble: Fabrosaurus, Buettneria perfecta,
Technosaurus, Staurikosaurus, Coelophysis, Petienosaurus, Rutiodon,
Sarcosuchus imperator, Postasuchus, Revueltosaurus callenderi, Chindesaurus,
as well as 4 unidentified prosauropod dentimorphs and at least 1
unidentified metoposaur.
Carnivore Specimens Described
Dimensions: 1 1/4 X 3/4 X 1/4
Shape: oval
Sphincter Fitness P
Color: dark brown thin layer around light center
Surface Texture: smooth, raised seam
Description: 2 X 3/32 dia. white bone inclusions on end (1A), side
by side
various rectangular and irregular thin bony fragments, spine or gastralia
like inclusions on end (1B), possible scale (1C, in.)
Picture
Dimensions: 1 1/2 X 3/4 X 3/8
Shape: Bone, raised seam
Sphincter Fitness N
Color: thin oily dark brown over light material
Surface Texture: conglomerate surface
Description: whole bone piece, 3 blade-like impressions in a
line (2A),
typical z-line (in.), deepest impressions along the z-line are along the
4/32 length lines, 2nd deep impression (2B, in.), 3rd blade-like zigzag at
bone end (in.) and opposing impression.
Picture
Dimensions: 1 3/4 X 3/4 X 1/2
Shape: bone, liquid, raised seam
Sphincter Fitness N
Color: thin oily dark brown over light material
Surface Texture: conglomerate
Description: solid bone with liquid end drip, 2 z-lines
coming to point
with opposing impression (3A), the lack of extruded material due to an
impact after formation suggests the impression was made in the bone, the
impression was possibly filled with liquid which ran distally when extruded,
gastralia are seen in the proximal end, paired peg-like impressions (in.)
Picture
Dimensions: 3/8 X 3/8 X 1/2
Shape: tubular, dimpled end
Sphincter Fitness P
Color: brown outer, white inner with round dark inclusions
Surface Texture: smooth with black globules
Description: gastralia concentrated at perimeter, paired
peg-like
impressions (in.)
Dimensions: 1 1/2 X 3/4 X 1/4
Shape: oval, dimpled end
Sphincter Fitness N
Color: light
Surface Texture: fibrous conglomerate
Description: 3/8 x 3/8 sheet of bony filamentary material
and surrounding
separate filaments, had thought these were from fish ribs, but this specimen
suggests alternative source, possibly gastralia, complete absence of
rectangular chips, these may be preserved sheets of gastralia
Dimensions: 1 1/4 X 1 X 3/8
Shape: oval with raised seam
Sphincter Fitness PD
Color: dark brown throughout
Surface Texture: smooth
Description: ribs with tubular cross section, 3 scales (6A,
in.)
Picture
Possible small coelosaur print (6B, in.)
Picture
Dimensions: 1 5/8 X 1 X 3/8
Shape: oval
Sphincter Fitness P
Color: dark outer coating on light material
Surface Texture: mostly scavenged, otherwise smooth
Description: Spear-like transparent shards, outer dark layer
eroded away,
given the coprolite was mostly liquid with scales and bones mixed it looks
like post-excretion predation, odd assemblage of many structures,
spine-like, rectangular (7A), and oval (7B) scale-like with concentric rings
and dimpled center, 2 traces of 3 teeth of blade-like impressions (in.)
Picture
Dimensions: 1 1/8 X 1/4 X 1/4
Shape: bone
Sphincter Fitness N
Color: bone color
Surface Texture: eroded
Description: could be whole bone but very degraded,
concentric rings on
end, bite marks on end (8A, in.), slash (8B, in.)
Picture
Dimensions: 1 1/4 X 1/2 X 1/2
Shape: teardrop, dimpled
Sphincter Fitness N
Color: dark brown on light
Surface Texture: conglomerate
Description: 2 definitive teeth marks on bone pieces (in.),
unassociated,
showing fossilization color variations one edges of marks, numerous finely
crushed bone fragments, numerous indefinite triangular impressions in
segments, possibly teeth marks, material appears to be actively processed in
the mouth, no association apparent.
Dimensions: 1 1/2 X 3/4 X 3/8
Shape: bone
Sphincter Fitness N
Color: brown oily coat on bone
Surface Texture: smooth
Description: end showing concentric bone-like structure, could be
theropod
bone, scaly outer layers, 4 bite marks (in.), nice deep bite (10A, in.)
Picture
Dimensions: 1 X 7/8 X 1/2
Shape: Bone
Sphincter Fitness N
Color: dark brown oily coat on bone
Surface Texture: conglomerate
Description: whole bone piece, several pairs of peg-like
impressions
uniformly spaced 1/16, appear to be made post-deposit, 2 pairs opposed on
opposite sides, one pair centered in compressed area of bone
Dimensions: 1 1/4 X 1/2 X 1/4
Shape: tubular
Sphincter Fitness P
Color: light
Surface Texture: conglomerate
Description: several shield-shaped scales or teeth mark
edges (12A),
gastralia, many pieces show scalloped edge, irregular shapes suggest
thorough processing, possible bite on the formed coprolite, suggests herd
members may have struck at anything that moved
Picture
Outer brown surface largely scraped off
Dimensions: 2 1/2 X 3/4 X 1/2
Shape: teardrop
Sphincter Fitness N
Color: brown on white
Surface Texture: conglomerate surface
Description: inclusions of crushed bone, numerous paired
peg-like
impressions
Dimensions: 1 3/8 X 1 1/4 X 1/4
Shape: bone
Sphincter Fitness N
Color: brown on white
Surface Texture: smooth
Description: large flat bone
Dimensions: 1 3/4 X 3/4 X 1/2
Shape: oval
Sphincter Fitness N
Color: light brown outer, dark brown core
Surface Texture: smooth
Description: looks like impressions of a toe claw (15A),
[possible fish
scales and ribs in mostly liquid mass, strange tar black layer, shield
scales
Picture
Dimensions: 1 3/8 X 1/2 X 1/4
Shape: oval
Sphincter Fitness P
Color: dark brown throughout
Surface Texture: conglomerate
Description: pair of bite marks demonstrating possible
genesis of shield
shaped fragments, blade-like, finely crushed bone
Dimensions: 1 3/8 X 7/8 X 3/8
Shape: oval, raised seam
Sphincter Fitness P
Color: light
Surface Texture: eroded
Description: mass of finely crushed thin material, possible
mammal bite in
effort to scavenge
Picture
Dimensions: 1 1/4 X 3/4 X 1/2
Shape: oval
Sphincter Fitness PF
Color: brown on white liquid
Surface Texture: conglomerate
Description: footprint and crushed coprolite (18A, in.),
large
accumulation of gastralia at center, surrounded by crushed bone, fine
example of tooth drag with peg-like teeth (18B, in.)
Picture
Dimensions: 1 1/4 X 3/8 X 1/2
Shape: oval
Sphincter Fitness N
Color: solid dark brown
Surface Texture: bubbles of varying size
Description: crushed scales or bone
Dimensions: 1 1/8 X 3/8 X 3/8
Shape: bone
Sphincter Fitness N
Color: white
Surface Texture: bone
Description: mostly scales with hard white matrix, tooth
drag on bone
fragment (in.), z-line (20A, in.)
Picture
Dimensions: 1 1/4 X 3/4 X 3/8
Shape: oval with tip
Sphincter Fitness N
Color: light
Surface Texture: eroded bone
Description: crushed filamentary material
Dimensions: 1 X 3/4 X 1/2
Shape: oval
Sphincter Fitness P
Color: white liquid
Surface Texture: smooth
Description: crushed bone with hard white matrix
Dimensions: 1 1/4 X 1/2 X 3/4
Shape: teardrop with dimple
Sphincter Fitness N
Color: white
Surface Texture: smooth
Description: large toe impression, liquid, tiny crushed
material
Dimensions: 1 3/8 X 5/8 X 1/4
Shape: teardrop with dimple
Sphincter Fitness P
Color: white
Surface Texture: smooth
Description: crushed bone or scale in white matrix
Dimensions: 1 1/4 X 1/2 X 3/8
Shape: teardrop with dimple
Sphincter Fitness N
Color: brown on outside
Surface Texture: conglomerate
Description: assortment of crushed bone
Dimensions: 1 1/8 X 5/8 X 1/2
Shape: teardrop with dimple
Sphincter Fitness PF
Color: light
Surface Texture: conglomerate
Description: fish ribs at center, crushed bone on outside,
interesting
traces on a bone fragment
Dimensions: 1 3/8 X 3/4 X 1/2
Shape: teardrop
Sphincter Fitness PF
Color: greenish patina
Surface Texture: smooth
Description: interesting impression next to long smooth edge
piece of
material, various scale-like inclusions
Dimensions: 7/8 X 1 3/8 X 1/2
Shape: teardrop
Sphincter Fitness N
Color: light brown over white
Surface Texture: conglomerate
Description: many shards of crushed bone
Dimensions: 1 1/4 X 3/8 X 1/4
Shape: tubular
Sphincter Fitness PD
Color: white
Surface Texture: eroded
Description: various small inclusions
Dimensions: 1 1/8 X 1/2 X 1/2
Shape: teardrop
Sphincter Fitness P
Color: brown on white
Surface Texture: smooth
Description: fine inclusions
Dimensions: 1 X 1/2 X 1/2
Shape: tubular
Sphincter Fitness P
Color: solid brown
Surface Texture: conglomerate
Description: fine inclusions
Dimensions: 1 X 1/2 X 1/2
Shape: tubular
Sphincter Fitness N
Color: brown on light
Surface Texture: conglomerate
Description: fine filament and bony inclusions
Dimensions: 1 X 3/8 X 3/8
Shape: oval
Sphincter Fitness N
Color: white
Surface Texture: conglomerate surface
Description: large chunks of bone
Dimensions: 1 1/8 X 1/2 X 1/4
Shape: oval
Sphincter Fitness PD
Color: dark brown on white
Surface Texture: smooth
Description: large amount of irregular bone inclusions
Dimensions: 1 1/2 X 1/4 X 1/4
Shape: tubular, raised seam
Sphincter Fitness N
Color: dark brown on light
Surface Texture: conglomerate
Description: appears to be exit shaping, some striations on
the exit and
raised edges axially
Dimensions: 1 3/8 X 3/8 X 3/8
Shape: teardrop, rounded
Sphincter Fitness N
Color: solid brown
Surface Texture: smooth
Description: liquid end, axis of gravity aligned with axis
of coprolite,
side bite due to predation
Picture
Dimensions: 1 1/8 X 3/8 X 3/8
Shape: teardrop with dimple on end
Sphincter Fitness PF
Color: dark brown on white
Surface Texture: conglomerate
Description: unique fibrous bony inclusions
Dimensions: 1 1/4 X 1/2 X 3/8
Shape: oval
Sphincter Fitness N
Color: dark brown on white
Surface Texture: conglomerate
Description: bone fragments around a solid bone center
Dimensions: 1 X 1/4 X 3/8 and 1 1/8 X 1/4 X 1/4
Shape: oval, tubular
Sphincter Fitness NN
Color: dark brown on white
Surface Texture: conglomerate
Description: oval: dense fibrous bone, tubular: bone fragment
Dimensions: 1 X 1/2 X 1/2
Shape: tubular
Sphincter Fitness PFDF
Color: light
Surface Texture: smooth
Description: mostly liquid
Dimensions: 1 1/48 X 5/8 X 3/8
Shape: bone
Sphincter Fitness N
Color: light
Surface Texture: smooth
Description: zigzag bite on bone associated with bone
compression and
opposing bite
Dimensions: 1 1/4 X 3/8 X 3/8
Shape: tubular
Sphincter Fitness DF
Color: light
Surface Texture: bony
Description: peg-like indentations in solid bone, possibly
phytosaurus
Dimensions: 7/8 X 3/4 X 1/4
Shape: oval
Sphincter Fitness PFDF
Color: light brown
Surface Texture: smooth
Description: unique plates of bone surrounded with liquid
and fragments
Dimensions: 1 X 1/4 X 3/8
Shape: tubular
Sphincter Fitness PD
Color: dark brown on white
Surface Texture: smooth
Description: large bone chunks, bite to coprolite with
opposing marks
Dimensions: 1 1/8 X 1/2 X 3/16
Shape: bone
Sphincter Fitness N
Color: light
Surface Texture: eroded
Description: mostly bone
Dimensions: 7/8 X 3/8 X 1/4
Shape: tubular
Sphincter Fitness PFD
Color: light
Surface Texture: eroded
Description: cell bone with end bite
Dimensions: 1 1/48 X 1/4 X 3/8
Shape: tubular
Sphincter Fitness D
Color: dark brown
Surface Texture: conglomerate
Description: fibrous inclusions
Dimensions: 1 1/4 X 3/8 X 3/8
Shape: teardrop
Sphincter Fitness N
Color: dark brown
Surface Texture: conglomerate
Description: inclusions
Dimensions: 1 1/8 X 5/8 X 1/4
Shape: oval
Sphincter Fitness PD
Color: dark brown throughout
Surface Texture: conglomerate
Description: bone fragments
Dimensions: 1 X 1/2 X 1/4
Shape: teardrop
Sphincter Fitness N
Color: white
Surface Texture: laminar, liquid
Description: possibly digested bone
Dimensions: 1 1/8 X 5/8 X 1/4
Shape: oval
Sphincter Fitness PD
Color: brown on light
Surface Texture: conglomerate
Description: large chunks in association, most chunks show
scalloped appearance
Picture
Dimensions: 1 1/2 X 1/2 X 3/8
Shape: tubular
Sphincter Fitness PD
Color: brown on light
Surface Texture: conglomerate
Description: fish ribs, large pieces of bone in association
Dimensions: 1 1/8 X 3/4 X 3/8
Shape: teardrop
Sphincter Fitness DF
Color: brown on light
Surface Texture: smooth
Description: center filled with gastralia, surface predation
Dimensions: 1 1/4 X 3/4 X 3/8
Shape: oval
Sphincter Fitness PF
Color: brown on light
Surface Texture: laminar
Description: surface scavenged
Dimensions: 1 X 5/8 X 1/2
Shape: teardrop with seam
Sphincter Fitness PF
Color: mostly light
Surface Texture: conglomerate
Description: few gastralia inside, bite in bone
Picture
Dimensions: 1 5/8 X 3/4 X 3/8
Shape: tubular
Sphincter Fitness PF
Color: brown on white
Surface Texture: conglomerate
Description: raised edge, bite with opposing and two others
Dimensions: 1 1/4 X 5/8 X 1/2
Shape: bone
Sphincter Fitness D
Color: brown coating
Surface Texture: conglomerate
Description: nice bite serrations
Dimensions: 1 3/8 X 1/2 X 1/2
Shape: bone
Sphincter Fitness N
Color: brown on white
Surface Texture: conglomerate
Description: huge bone bite
Dimensions: 1 3/8 X 5/8 X 1/2
Shape: teardrop
Sphincter Fitness N
Color: brown on white
Surface Texture: smooth
Description: many nice paired peg-like impressions associated
with scavenging showing all aspects of claws
Picture
Dimensions: 1 X 1/2 X 1/4
Shape: oval, raised seam
Sphincter Fitness DF
Color: dark brown throughout
Surface Texture: lumpy
Description: bone/scale inclusions
Dimensions: 1 1/8 X 1/4 X 3/8
Shape: bone
Sphincter Fitness N
Color: brown on white
Surface Texture: smooth
Description: bone bite
Dimensions: 1 X 1/4 X 3/8
Shape: tubular
Sphincter Fitness P
Color: dark brown throughout
Surface Texture: conglomerate
Description: bone chips
Dimensions: 1 X 1/2 X 1/2
Shape: tubular
Sphincter Fitness DFPF
Color: brown throughout
Surface Texture: smooth
Description: paired peg-like impressions associated with
Predation, fish ribs
Dimensions: 7/8 X 1/2 X 1/2
Shape: teardrop
Sphincter Fitness N
Color: brown on light
Surface Texture: laminar smooth
Description: paired peg-like impressions associated with
predation, odd
semi-circular bite
Dimensions: 1 X 3/4 X 1/2
Shape: teardrop
Sphincter Fitness D
Color: brown on light
Surface Texture: conglomerate
Description: gastralia, bone/scale
Dimensions: 1 1/2 X 5/8 X 5/8
Shape: tubular, raised seam
Sphincter Fitness N
Color: brown on light
Surface Texture: smooth
Description: distal bite
Dimensions: 1 X 5/8 X 3/8
Shape: tubular
Sphincter Fitness DFPF
Color: white
Surface Texture: conglomerate
Description: could be whole bone
Dimensions: 1 1/42 X 1/2 X 1/2
Shape: teardrop with dimple
Sphincter Fitness PF
Color: white
Surface Texture: smooth
Description: some evidence of bubbles
Dimensions: 1 1/48 X 1/2 X 3/8
Shape: oval
Sphincter Fitness PF
Color: brown on white
Surface Texture: conglomerate
Description: paired peg-like impressions
Dimensions: 1 3/8 X 1/2 X 1/2
Shape: tubular, raised seam
Sphincter Fitness PF
Color: brown throughout
Surface Texture: conglomerate
Description: inclusions
Dimensions: 1 1/4 X 3/16 X 3/8
Shape: tubular
Sphincter Fitness N
Color: brown on white
Surface Texture: smooth
Description: inclusions
Dimensions: 1 3/8 X 3/8 X 1/4
Shape: teardrop
Sphincter Fitness N
Color: white
Surface Texture: smooth
Description: footprint
Dimensions: 1 X 1/4 X 3/4
Shape: oval
Sphincter Fitness PF
Color: white
Surface Texture: bone
Description: solid bone, teeth at break
Dimensions: 1 X 1/2 X 5/8
Shape: oval, raised seam
Sphincter Fitness P
Color: brown throughout
Surface Texture: conglomerate
Description: bone with bite marks
Dimensions: 1 1/42 X 1/2 X 1/2
Shape: tubular
Sphincter Fitness PF
Color: brown on white
Surface Texture: smooth
Description: liquid with inclusions
Dimensions: 1 1/2 X 1/4 X 5/8
Shape: oval
Sphincter Fitness PD
Color: light
Surface Texture: conglomeration
Description: paired peg-like impressions
Dimensions: 1 3/8 X 1/2 X 3/4
Shape: oval
Sphincter Fitness P
Color: brown on light
Surface Texture: smooth
Description: inclusions
Dimensions: 1 5/8 X 5/8 X 3/8
Shape: tubular
Sphincter Fitness N
Color: brown on white
Surface Texture: bone
Description: solid bone, major bite mark on marrow
Dimensions: 1 1/4 X 1/2 X 3/4
Shape: oval, raised seam
Sphincter Fitness PF
Color: brown throughout
Surface Texture: smooth
Description: large tooth bite at end
Dimensions: 1 X 3/8 X 3/8
Shape: teardrop
Sphincter Fitness N
Color: white
Surface Texture: smooth
Description: inclusions
Dimensions: 1 1/2 X 1/2 X 3/8
Shape: tubular
Sphincter Fitness P
Color: brown throughout
Surface Texture: smooth
Description: inclusions
Dimensions: 1 1/8 X 1/2 X 1/4
Shape: bone
Sphincter Fitness N
Color: white
Surface Texture: fractured
Description: hallow bone, bite crush
Dimensions: 7/8 X 1/2 X 1/2
Shape: teardrop
Sphincter Fitness PF
Color: brown on white
Surface Texture: conglomeration
Description: inclusions
Dimensions: 1 1/4 X 1/2 X 5/8
Shape: tubular
Sphincter Fitness P
Color: brown on white
Surface Texture: smooth
Description: included tooth, could be mammalian,
Surface covered with paw marks/scrapes
Dimensions: 1 3/4 X 3/8 X 3/8
Shape: tubular
Sphincter Fitness PD
Color: white
Surface Texture: conglomeration
Description: solid bone, bone chips are irregular not
square, conical bite
marks are indicated showing radial fractures, concentric layered bone ends
Picture
Dimensions: 1 1/8 X 5/8 X 3/8
Shape: oval, raised seam, dimple
Sphincter Fitness PF
Color: brown on white
Surface Texture: smooth
Description: gastralia and shield scale, heavily gnawed on
one side only,
crushed shards of bone
Picture
Dimensions: 1 3/8 X 1/2 X 3/4
Shape: teardrop
Sphincter Fitness N
Color: brown on white
Surface Texture: smooth
Description: degraded solid bone, appears bone came off in
layers, could
be due to bite or digestive process
Dimensions: 1 X 5/8 X 3/8
Shape: oval
Sphincter Fitness P
Color: dark brown
Surface Texture: smooth
Description: large bone inclusion, 1/4 round, rest liquid
brown, possible
toe print
Dimensions: 1 1/48 X 1/2 X 3/8
Shape: tubular
Sphincter Fitness P
Color: white
Surface Texture: eroded
Description: solid bone, one bite on end with 2 teeth
Picture
Dimensions: 1 1/4 X 1/2 X 3/8
Shape: tubular
Sphincter Fitness PF
Color: dark with light center
Surface Texture: conglomerate
Description: large bone pieces, center contains folded
gastralia
Dimensions: 1 1/4 X 1/2 X 3/4
Shape: oval
Sphincter Fitness N
Color: brown on white
Surface Texture: conglomeration
Description: rare folded or associated
Dimensions: 1 1/4 X 1/2 X 5/8
Shape: oval
Sphincter Fitness DP
Color: white
Surface Texture: fractured
Description: solid bone with bite marks on end, side
glancing bite,
intersecting bites, large pointed teeth
Strike 1 Strike 2 Strike 3
Picture
Dimensions: 1 1/2 X 1 X 1/4
Shape: oval
Sphincter Fitness P
Color: dark brown
Surface Texture: smooth
Description: footprint with clear claw marks, fragmented bone
Picture
Dimensions: 1 3/8 X 1/4 X 5/8
Shape: oval with dimple tip
Sphincter Fitness P
Color: white
Surface Texture: eroded bone
Description: bone with concentric layers, bites with
opposing marks and 2
other dragging slash cuts
Picture
Dimensions: 1 1/4 X 1/2 X 3/4
Shape: oval with rounded tip
Sphincter Fitness P
Color: brown on white
Surface Texture: smooth
Description: liquid coating on one side, mostly fractured
bone, no fish,
largest bone piece 1/4 X 1/4, black oily globules
Dimensions: 1 1/4 X 1/4 X 3/4
Shape: oval with rounded tip
Sphincter Fitness PF
Color: brown on white
Surface Texture: laminar mostly homogenous, striations
Description: fish ribs/gastralia, white material coated with
dark brown
oily layer, bone fragments,
Dimensions: 1 X 1/2 X 3/8
Shape: teardrop
Sphincter Fitness P
Color: brown throughout
Surface Texture: laminar
Description: mostly liquid with some bone fragments (thin),
uniform
rhombus scales 2/32 X 1/32
Picture
Dimensions: 1 1/2 X 1/4 X 3/8
Shape: tubular
Sphincter Fitness P
Color: brown on white
Surface Texture: conglomeration
Description: mostly bone but with one side with liquid and
apparent
bubbles, scales mostly rhombus with concentric growth rings
Picture
Dimensions: 1 1/2 X 1/8 X 3/8
Shape: teardrop
Sphincter Fitness P
Color: brown on white
Surface Texture: smooth
Description: mostly fish scales, rhombus with concentric
rings, gastralia
or ribs, 3 pronounced gnaw areas on coprolite
Dimensions: 7/8 X 1/2 X 3/8
Shape: tubular
Sphincter Fitness PD
Color: brown on white
Surface Texture: smooth
Description: bite at cut, bone surrounded by bone fragments,
second strike
with cross cutting side glance, second end cut, looks to be leg bone
possibly tibia
Strike 1 Strike 2 Strike 3
Picture
Dimensions: 1 X 1/4 X 3/16
Shape: tubular
Sphincter Fitness P
Color: brown throughout
Surface Texture: conglomerate
Description: finely ground bone fragments with brown oily
coating, layered
in cross section but not bone, notable fragment illustrated below
Picture
Dimensions: 1 3/16 X 1/4 X 3/8
Shape: tubular
Sphincter Fitness N
Color: light
Surface Texture: eroded
Description: highly eroded solid bone, possible conical
small tooth
impression, no bone flakes
Dimensions: 1 1/2 X 5/8 X 1/4
Shape: oval with seam
Sphincter Fitness N
Color: brown o white
Surface Texture: conglomerate
Description: one side scooped out or eaten
Dimensions: 1 3/4 X 7/8 X 5/8
Shape: oval with seam
Sphincter Fitness P
Color: brown on white
Surface Texture: conglomerate
Description: inclusions
Dimensions: 1 1/4 X 3/4 X 3/4
Shape: bone
Sphincter Fitness PD
Color: brown on white
Surface Texture: laminar
Description: big tooth mark (1/4) fracturing bone in
concentric
sheets
Dimensions: 1 1/2 X 1/2 X 1/2
Shape: teardrop
Sphincter Fitness P
Color: light
Surface Texture: smooth, laminar
Description: high detail toe claw print
Picture
Dimensions: 1 3/16 X 1/2 X 1/2
Shape: tubular
Sphincter Fitness DF
Color: light
Surface Texture: smooth
Description: few inclusions
Dimensions: 1 7/8 X 5/8 X 5/8
Shape: tubular
Sphincter Fitness PD
Color: light
Surface Texture: fractured
Description: could be whole bone highly predated, conical
teeth marks in
many locations, possible phytosaur
Character Statistics
The statistics here describe the 109 carnivore coprolites of the survey.
They are subdivided into 4 shape categories: 13% (14) Bone, 33% (36) Oval,
30% (33) Tubular, and 24% (26) Teardrop. The color of the coprolite
(excluding bone type) relative to shape is given in the table below.
Coprolite Color Vs Overall Shape (Excluding Bone)
% Tube (N) % oval (N) % teardrop (N)
dark throughout 27% (9) 31% (11) 15% (4)
dark on light 39% (13) 44% (16) 50% (13)
Light throughout 33% (11) 25% (9) 35% (9)
Sphincter-related coprolite end shaping (excluding bone type) relative to
overall shape is given in the table below.
End Shape Vs Overall Shape (Excluding Bone)
Sphincter Sufficiency* % Tube (N) % oval (N) % teardrop (N) All
Shapes
P or PF 39% (13) 53% (19) 42% (11) 45%
D or DF 9% (3) 3% (1) 8% (2) 6%
N 21% (7) 25% (9) 50% (13) 31%
DP, DFPF 30% (10) 19% (7) 0% (0) 18%
*See Character Definitions
The prevalence of coprolite with well-formed proximal and distal ends
(Sphincter Sufficiency = N), correlates with shape. As the shape transitions
from Tubular to Oval to Teardrop the incidence of well-formed shape
increases from 21% to 50% of coprolites within their groups and among all
coprolites 7% to 14%.
Hypothetical Sphincter Tension (T) Along Coprolite Axis (Z)
Fifty-two of 109 (48%) of all coprolites displayed some type of
organism-specific impressions. These organisms fall into two groups, those
forming the coprolites and those interacting with them after formation.
These two groups are not mutually exclusive.
Impressions in Coprolite
Impressions % Oval (N) % Tube (N) % Teardrop (N) % Bone (N)
On Coprolite (Post) 44% (11) 24% (6) 28% (7) 4% (1)
On Contents (Pre) 14% (4) 21% (6) 17% (5) 48% (14)
Assuming firmness of meal correlates with firmness of coprolite than we
would expect Pre preservation to increase with coprolite firmness and Post
preservation to decrease with coprolite firmness. Both sets of data put the
shape characters in the following order:
Increasing Coprolite Hardness -->
Oval --> Teardrop --> Tubular --> Bone
It is admittedly difficult to draw sharp distinctions between one shape
character and another. It may be more productive to think of just two types
based on content. Since content likely determines hardness and to some
extent shape, especially when bone passes through the digestive tract in
tact. Direct observations of the coprolites shows a continuum of digested
bone states coinciding with an evolution of shape from bone-like to tubular,
to even oval, especially if the bone has this shape to begin with. It is
difficult to make assumptions about digestive states of solid or associated
bone since many coprolites consists of very hard bone like matter that shows
liquid-type shaping forms. Thus the data presented here is based on strict
geometrical measures and not suppositions about the state of the digested
contents.
Paired impressions were strongly correlated with Post preservation and
Z-lines were strongly correlated with Pre preservation.
Impression Type Specificity to Time of Formation
Impression Type On Contents (Pre) On Coprolite (Post)
Paired impressions 0 8
z-lines 16 2
If we assume as hypothesized below in Paired Impressions, that the maker of
the paired impressions was a juvenile form of the maker of the z-lines then
this table supports this conclusion. Cross interaction occurs where z-lines
are found in Post condition, but paired impressions are not seen on the
digested contents. This finding also suggests the z-line mechanism involved
a greater force than the paired impression mechanism.
The table below shows the Paired Impressions occur predominately in the
softer Oval and Teardrop shape types and the Z-line Impressions occur
predominately in the harder Tubular and Bone shape types.
Impression Type Specificity to Shape of Coprolite
Impression Type % oval (N) % tubular (N) % teardrop (N) % bone (N)
Paired 25% (2) 25% (2) 38% (3) 12% (1)
z-lines 22% (4) 28% (5) 6% (1) 44% (8)
Impression Type Specificity to Hypothetical Hardness of Coprolite
Impression Type Soft % teardrop/Oval (N) Hard % bone/Tubular (N)
Paired 63% (5) 37% (3)
z-lines 28% (5) 72% (13)
Discussion
Paired Impressions
These surface markings are commonly encountered as pairs of peg-like
impressions in the surface of the coprolite, and less commonly in
association
with a third impression. The orientation is more often perpendicular to the
surface, although skew impressions were observed (see Sample). When observed
in skew, no additional features are noted except for extension of the
peg-like geometry. The impressions are frequently shallow, and usually less
than 2 mm below the surface. The walls of the impressions are substantially
parallel and the bottoms flat.
Hypothetical origins include: foot claws, hand claws, teeth, burst bubbles,
eroded inclusions (sand), vegetation, insect coprophagy. Foot claws are
ruled out on the basis that no other elements of the foot anatomy were
observed in association; and given the load bearing requirements placed on
this part of the anatomy. With respect to teeth, the paired structure and
geometry of the impressions suggests the paired, peg-like, prominent
incisors common among Permian reptiles, e.g., Captorhinus. The chronology
and absence of opposing bite marks is problematic. These marks have also not
been seen along transverse fractures. The almost exclusive paired nature of
these marks rules out random origins such as burst bubbles or eroded surface
particulate. Although plant origins can less convincingly be ruled out,
generally in plants if there is a first level structure, i.e., pairing, then
there are higher level structures as well. The fractal nature of plant
morphology is well known ferns are often cited examples. Because the paired
structures are randomly distributed, plant origin is less likely. Insect
pincers have proximal pivot points that make orthogonal entry into the
coprolite surface unlikely. In addition, no other traces are observed in
association, e.g., foot prints, thorax impressions.
In considering hand claws, it is noted that evidence of Coelurosaurian
coexistence in the form of teeth is prevalent. Coelophysis is the dominant
example. Further, a single 4 mm long hand claw matching the marks observed
was recovered at the site. In considering the coelurosaurian anatomy,
generally there are two approximately equi-length primary fingers.
Coelophysis, for example, possesses a reduced digit 1, primary digits 2 and
3, and a rudimentary digit 4. Compsognathus possesses paired digits 1 and 2
and reduced digit 3. Ornitholestes posses reduced digit 1 and paired digits
2 and 3. The distal ends of Coelurosaurian hand claws are blunter than the
toe claws, and possess peg-like extensions.
One can infer from the absence of impact modification of the coprolite a
hard composition soon after expulsion. The exact drop height is unknown, but
the accumulation of material in a teardrop shape in many coprolites suggests
the axis of gravitation force was aligned with the axis of the coprolite,
suggesting a separation between coprolite and supporting structures, i.e.,
the ground. Assuming a minimum height of 0.3 m and coprolite volume of 5 cc
and density greater than 1 g/cc, then the potential energy absorbed upon
inelastic impact is given by
PE = mgh = 0.005 kg X 10 m/s2 X 0.3 m = 0.015 J (minimum)
Assuming the impact distorts the coprolite less than 0.001 m, than the force
imparted to the coprolite is
F = PE/d = 15 N
Assuming an impact area of less than 25 mm2, then the minimum pressure
required to create an impression in the coprolite would be 0.6 N/mm2. For
two pairs of claws, each with 4 mm2 surface area the force required would be
9.6 N (1N force = 2.25 lbs force). In terms of pressure, this force
represents more than 844 PSI. These calculations give a lower bound on the
forces required to deform a coprolite immediately after formation, and
intervening hardening would raise this minimum.
In most of the specimens there are rarely more than 1 or 2 paired
impressions. A notable exception is Sample XX. The association of these
paired impressions with tooth impressions on the coprolite is also absent.
Other impressions were randomly distributed and of varying size, yet
circular in cross section and shallow. These were ascribed to liberation of
trapped or formed gases and loss of surface inclusions, principally sand or
fine, round particulate. No evidence of burrows indicating consumption of
organic materials and nutrient recycling by macroscopic organisms were
observed. Coprophagy traces were observed by others in the Chinle Formation
of the Petrified Forest National Park (Chin and Gill, 1996, Wahl et al,
1998), but not in this survey.
Claw Impressions
Impressions of mammalian claws are found among coprolites lacking bony
inclusions, while none are found on bone included specimens. The range and
abundance of geometric forms do not differ for the two types. Since form is
dictated in part by composition, it is not easily asserted that the trace
impressions are mitigated on the basis of coprolite composition.
The impressions are comprised of three approximately collinear digit prints.
The prints are terminated in slender, sharp claws, in many cases the prints
are only of the claw portion.
Mammal-like reptiles were abundant in the late Permian and early Triassic.
However, their number declined sharply in the Late Triassic. The decline of
the mammal-like reptiles coincided with the rise of the dinosaurs and
mammals. Early mammals are universally described as small, shrew-like,
probably nocturnal, insectivorous creatures. The present evidence supports
nocturnal, insectivorous behavior. Nocturnal, because the claw impressions
are most abundant in locations of large coprolite concentration, suggesting
a high activity environment accessibly only at night. Insectivorous, because
fresh dung would likely concentrate insect populations, and less evidence of
direct predation on the coprolites is found.
The present attribution of mammalian origin to the claw prints is based on
their characteristic rodent-like size and structure. The megazostrodon is
one of the better-preserved mammals of the Late Triassic. The strongest
evidence that these claw impressions are mammalian derives from the
observation that teeth marks in association with some claw impressions
depict a precision bite characteristic of mammals.
The present impressions indicate a megazostrodon-like mammal, perhaps
Microconodon sp., because of the evidence of nocturnal habit, sharp spiky
teeth, and slender sharp claws. The Microconodon has been found in New
Mexico Triassic exposures.
Digestive States and Predation Dynamics
It was noted in the statistical portion of this survey that anecdotally
there appears to be a continuum of digested states with respect to whole
bone inclusions. Lean times may have produced coprolites with bone in highly
digested states and more liquid composition. It should be noted that while
this spectrum of digestive states appears to be relevant to whole bone
inclusions, the same spectrum of degraded states is not seen for highly
processed material in the conglomerate state. The particulate in these
coprolites appears to be quite fresh with sharply demarcated edges.
Similarly, whole bone inclusions are frequently encased in crushed bone
conglomerations. Comparing the encapsulating conglomeration to the whole
bone, one notices a marked difference in digestive states. While some of the
elements of the conglomeration are attributable to fish scale, which may be
less digestible, there are many examples of whole bone inclusions
disintegrating into the characteristic rectangular fragments. It is
therefore, a reasonable hypothetical to suggest the crushed material passed
more quickly through the digestive tract. Prey success, therefore, may
select the coprolite characters.
Further point of interest: Coprolite volume or length may relate to degraded
states, color, and shape.
Literature Cited
Ash, S.R. 1978. Coprolites. In Ash, S. R. (ed.), Geology, Paleontology and
Paleoecology of a Late Triassic Lake, Western New Mexico. Brigham Young
University Geology Studies 25:69-73.
Thulborn, R. A. 1991. Morphology, preservation and palaeobiological
significance of dinosaur coprolites. Palaeogeography, Palaeoclimatology,
Palaeoecology, 83:341-366.
Wahl et al. 1998. Vertebrate Coprolites and Coprophagy Traces, Chinle
Formation (Late Triassic), Petrified Forest National Park, Arizona.
Technical Report NPS/NRGRD/GRDTR-98/1, pp. 144-148.
Webber, D. J., and G. C. Lawler. 1978. Lipid components of the coprolites.
In Ash, S. R. (ed.) Brigham Young University Research Studies, Geology
Series, 25:75-87.