The Lopha lugubris lineage is the predominant species group of ostreids in the Middle and Upper Turonian (Upper Cretaceous) sediments of the western interior and western Gulf Coast. The upper and lower contacts of the Juana Lopez are unconformable over much of its geographic range in Colorado and northern New Mexico.
NO. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP KAUFFMAN 7 The Austin has been considered totally Coniacian in the past, although
HISTORY
8 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 overlooked the different stratigraphic ranges of the first two forms
STUDY OF FOSSIL OSTREIDAE
NO. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP — KAUFFMAN 9
BELLAPLICATA BELLAPLICATA
BELLAPLICATA NOVAMEXICANA
The chemical environments of two very similar sandstones may have been completely different and may have greatly influenced the type of shell produced in each area.
EVOLUTION
12 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48
LU6UBRIS
BELLAPL8CATA NOVAMEXICANA
B L. BELLAPLICATA NOVAMEXICANA
LUGUBRIS BELLAPLICATA BELLAPLICATA
The plicae do not divide normally (fig.6bandc) and their number is relatively constant everywhere on the mature part of the shell. Note general decrease in overall convexity, ventral migration of the high point of the valve (illustrated by vertical lines through cross-sections) through time.
14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 in measuring them do not vary significantly from one point to an-
NO. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP — KAUFFMAN 15
LEFT VALVE
BELLAPLICATA- BELLAPLICATA
LUGUBRIS
BELLAPLICATA
NOVAMEXICANA
Reduction in the size (width, depth) of the auricular sulci, relative to shell size (fig. 5d,6a). Increase in the absolute height and relative extent of the smooth stage on the early shell, especially in left valves.
NO. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP KAUFFMAN 19
NUMBER OF DENTICLES IN 5 MM LENGTH
LENGTH OF LEFT VALVE (MM)
Most of the trends that are thought to be selected in the field of environmental change relate to improving hydrodynamic stability, strength and anchorage of the shell. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP KAUFFMAN 23increasing the relative size of the attachment area, the overall size.
NO. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP KAUFFMAN 23 increase in the relative size of the attachment area, the general size
These two forms coexist in the wide variety of environments from which the species is known, but there is a marked increase in the relative percentage of individuals with large attachment areas in shallow-water sediments deposited under high-energy wave and current conditions (Codell Sandstone) . This limitation in food intake is related to the below-average size of many shallow-water epifaunal pelecypod species that develop to normal proportions in quiet, offshore waters.
SHELL MORPHOLOGY
ANS —Anterior slope of the valve (includes the lower part of the anterior auricle where it is developed); part of the shell between the dorsal and anteroventral slopes and the ridge (Fig. 10c). CR —Valve ridge; uppermost area of valve, either slightly convex or almost flat, located dosocentrically (Fig. 10c).
NO. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP — KAUFFMAN 27
SS—Smooth stage; that part of the beak, umbo (in many cases the entire umbo) and adjacent parts of the valve that have no radiating connections (Fig. 10b). The width of a single valve is measured in a similar manner: between the highest point of the valve and the commissure plane (or if the beak is overhanging, the plane running along the most projecting edge).
SYSTEMATIC PALEONTOLOGY
SC - Subcardinal cavities; shallow^ re-entrances of the valve floor beneath the structures of the cardinal area, chiefly beneath the lateral cardinal plates of the medial fold. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP — KAUFFMAN 2g Adjacent layers of gently inclined lamellae usually with opposite dips. The name Alectryonia is usually used for oysters with the characteristics of Lopha, and the two are objective synonyms, having the same type species.
The popularity that Alecryonia has achieved in recent years stems from Stenzel's adoption of the name in lieu of Loph (1947, p according to the rules of the International Commission on Zoological Nomenclature that existed at the time of his work.
30 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 heim was validly proposed in 1807 before Lopha was validated with
NO. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP KAUFFMAN 3
32 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 Table 1
NO. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP — KAUFFMAN 33
R Length of hinge line (LHL) 3
R Maximum diameter of muscle scar
Concentric ornament between margin of attachment area and plicate portion of valve with faint growth lines, microlamellae, more rarely with crowded, rough, flat, large overlapping lamellae. Beak and early umbonal area smooth; central, ventral portions of umbo marked with faint growth lines, less commonly with small, low undulations and microlamellae, rarely with scattered coarse lamellae or undulations on ventral umbo. Plicae differently developed on minority specimens (pi.. 7), never covering more than half of the valve, usually restricted to margin 5.
Cardinal area.— Composed of subcentral resilifer and/or mid-cardinal fold (right valve), bordered laterally by flat to moderately curved lateral cardinal plates or folds for ligamentous attachment.
36 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48
ONTOGENY
Gerontic stage characterized by crowded, coarse large lamellae, small undulations near margin, marking great reduction in rate of shell growth, sharp changes in concentric decoration marking ephebian-gerontic boundary. Convexity.- On the right valve (Fig. 3b), gradual increase in the degree of outward curvature from nepionic through early neanic, greatest in late neanic, early ephebic, gradually to abruptly decreasing through late ephebic. Internal structures. - The expansion rate of musculature, the hinge line, constant and less rate of shell growth during neanian and early ephebian stages, gradually tapered off during late ephebian and gerontic.
Extent of denticles relative to shell height and density of denticles, greatest during neanic, early ephebian stages, gradually decreasing later.
REMARKS
NO. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP — KAUFFMAN 39
SHELL HEIGHT (MM)
LENGTH OF VALVE(MM)
LENGTH OF VALVE (MM)
VALVE HEIGHT (MM)
NO. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP — KAUFFMAN 4I
Consistency in the placement of the muscle scar and the cardinal characters on both valves, regardless of winding direction, indicates that attachment is always at the left valve, as in other ostreids. At Huerfano Park, Colo., fragments doubtfully referable to this species were collected in the upper part of the "Pugnellus Sandstone" (Codell Sandstone Member, CarHle Shale; upper part of zone of Collignoniceras hyatti) associated with L. Hattin's report on this species from the Blue Hill Shale Member of Kansas (lower part of the Collignoniceras hyatti Zone; 1962, p.84) is based on a typical specimen of L .
Anterior, ventral margins straight to slightly curved; ventrolateral margins moderately curved; posterior margin with moderate convex curvature in absence of auricle, moderately concave below auricular muscle.
NO. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP — KAUFFMAN 45
46 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 Rarely, dorsolateral margins moderately rounded or steeply inclined
Place most prominent centrally and ventrally on valve; spinose, subnodose, grooved on rare left valves where cut by coarse, raised concentric lamellae (pi. Lateral cardinal plates subequal to moderately unequal (on shells with prominent posterior otic muscle), posterior plate largest; each plate larger than resiliferin most valves. Narrow marginal cardinals passages.commonly developed between lateral cardinal plates and margin of valve, most common on left valves.
Majority of right valves with low resilifer bounded ventrally by a raised lip (partial mid-cardinal fold).
NO. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP — KAUFFMAN 49
50 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 characterized by scattered coarse lamellae on left valve, some raised
NO. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP — KAUFFMAN 5
16.—A, Ontogeny of the muscle scar in Lopha hellaplicata bellaplicata (Shumard), showing the relationship between the greatest diameter of the posterior adductor muscle of the scar and the height of the valve. Axis slightly curved in nepion shell, more moderately curved during nean and early ephebian development, slightly curved, becoming nearly straight through ephebian and gerontic stages. The length of the hinge line, which gradually increases through the middle ephebe stage, is slightly less than the total lateral expansion of the valve; between the late febic and gerontic stages, hinge line growth continues, but at a rate higher than the rate of lateral valve expansion (Fig. 17c).
Density of denticles decreased at a variable rate through growth from shell to gerontic stage (fig. 17a), where it remained stable.
54 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48
NO. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP — KAUFFMAN 55
This possibility is not presented by other members of the group, which occur in more uniform lithologies. Thickening of the shell appears to be an adaptation to this more active environment, its main function being to strengthen the valves. Specimens from New Mexico, found as gypsum replacements in dark shale, are typical of the species.
Most of the specimens from Colorado, although smaller, are typical of the species and morphologically very comparable to the Texas forms (compare pi.
NO. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP — KAUFFMAN 57
58 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 (Codell Sandstone Member) of the Carlile Shale, where it is found in
I48 inner auricle separated from the main part of the shell by a broad, shallow, indistinct auricular sulcus, generally a widened interplical sulcus or 2 sulci with the intermediate applique much reduced. Right valve flat to slightly curved; convexity greatest in umbonal region; The flanks are flat, rarely concave near the margin when the ventral edge is turned upwards. Lower umbo and part of valve between attachment scar and spot flanks marked with numerous fine, crowded, overlapping lamellae, fine growth lines.
Concentric decorations on the pleated part of the valve, consisting of numerous closely packed, equally to irregularly spaced, fine to medium.
62 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 REMARKS
6 OSTERS OF THE LOPHA LUGUBRIS GROUP — KAUFFMAN 63would occupy an ecological niche so well defined that two would occupy an ecological niche so well defined that two closely related species or subspecies would be to live together and compete. Stratigraphic and Geographic Occurrence.—^ The variety occurs throughout the Middle Turonian "Pugnellus Sandstone" (Codell Sandstonemember) of the CarlileShaleat and 61 localities at Huerfano Park, Colo.
64 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 Table 5
R Number of plicae (total) : ,
NO. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP — KAUFFMAN 65 Table 5
Early to middle neanic in the left valve marked by a few coarse crowded growth lines, lamellae and ridges just before sudden development of plicae. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP KAUFFMAN 69 rounded with age through the middle Ephean phase; becoming lower, rounded with age through the middle Ephean stage; becomes lower. The only observable morphological differences between forms from the two states that may be environmentally controlled are (1) the sharp plicaeon of many Colorado specimens (pi. 7, fig. 11) and (2) the tendency of some Colorado specimens to have a ventral.
Below this unit, in the upper part of the Blue Hill Shale Member, septarian limestone concretions contain scattered but characteristic examples of the subspecies nova-mexicana (pi.
COLLECTING LOCALITIES
6 OYSTERS OF THE LOPHA LUGUBRIS GROUP KAUFFMAN Jl zone of CoUignoniceras hyatti (Stanton) (Late Middle Ttironian), well below the occurrence of L. The two forms do not have overlapping ranges in this area, although rare individuals in the transition between them occur as marginal variants of each form. If future assemblages show this to be true offshore in the Western Interior, these ostreides will have special significance as stratigraphic markers, since the fauna of these two units overlaps in almost every other respect.
72 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48 associated matrix at what stratigraphic level they were obtained
NO. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP — KAUFFMAN 73
74 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48
7539 (same as listed for Lopha lugubris) - Eagle Ford Shale, layer no. 1, Texas Portland Cement Company quarry, 2.5 miles east of EagleFord, Dallas County, and 3 miles west of Trinity Riverat Dallas, Tex. 10046-Eagle Ford Shale, 7 miles west of Palestine in salt works, on ridge g miles northeast of plant, Texas. 11732-3 upper feet of Eagle Ford Shale, at the Texas Portland Cement plant quarry west of Dallas, Tex.
12942—Eagle Ford Formation, Palestine Salt Dome, east of salt flats, at Old Lodge, Anderson County, Texas.
76 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48
BlueHill ShaleMember, Carlile Shale, Colorado Group, zone of septarian limestone concretions in upper 10 feet of section, 1 mile east of Williams Creek, ^ mile south of unimproved dirt road, Wl/2 NEl/4. BlueHillShaleMember, CarlileShale, Colorado Group, zone of septarian limestone concretions in upper 20 feet of section, along Fort Hays Limestonehogbacksouthofan unimproved land road, 0.8 mile SE of Maes School, NWl/4 NEl/4 sec. BlueHill Shale Member, Carlile Shale, Colorado Group, zone of septarian limestone concretions in upper 25 feet of member, below.
Blue Hill Shale Member, Carlile Shale, Colorado Group, septarian limestone concretions in upper part of section, 1 mile N of Arkansas River, on slopes surrounding dry branch, SEl/4 NEl/4.
LITERATURE CITED
Upper Blue Hill Shale Member, Carlile Shale, Colorado Group, in 2-inch limestone overlying cone-in-cone, Septarian Limestone Zone, Collignonicerashyatti area, stream 1.3 to 1.5 miles northwest of Red Wing, on Jones' Cattle Ranch Company,. Blue Hill Shale Member, Carlile Shale, Colorado Group, a Septarian limestone concretion zone in the upper 15 meters of the member, just below the Juana Lopez-FortHaysLimestonehogback, 2-3 miles north of Thatcher, Colo., 50 to 100 yards east of an improved dirt road that runs north of the convenience store and Thatcher School. Contributions to the Tertiary faiuia of Florida, with special reference to the Silex beds of Tampa and the Pliocene beds of the Caloosahatchee River, including in many cases a complete revision of the generic groups discussed and their American Tertiary types.
NO. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP KAUFFMAN 79
EXPLANATION OF PLATES
NO. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP — KAUFFMAN 83
84 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 1 48
NO. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP — KAUFFMAN 85
Due to the attachment scar and the round nature of the plicae (worn), the nature of the valve is identical to that of L.bellaplicata bellaplicata depicted in plates 3 and 4; hypotype (of L. bellaplicata bellaplicata) from the upper Eagle Ford Shale, Collin Coimty, Tex. Lateral view of an unusually flat left valve with abnormal prosocline inclination, a hypotype from the upper Eagle Ford Shale, Dallas County, Tex. Lateral view of an adult left valve showing extensive plicae branching and an unusually reduced posterior auricle; a hypotype from the Upper Eagle Ford Shale, 4 miles east of Eagle Ford, Dallas County, Tex.
Lateral view of large left valve showing large attachment scar, otherwise characteristic of the species; hypotype from the upper Eagle Ford.
NO. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP — KAUFFMAN 87
88 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48
NO. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP — KAUFFMAN 89
90 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48
NO. 6 OYSTERS OF THE LOPHA LUGUBRIS GROUP — KAUFFMAN 9I
92 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I48
PLATES
SEE EXPLANATION OF PLATES AT END OF TEXT.)
SEE EXPLANATION OF PLATES AT END OF TEXT
BELUAPLICATA BELLAPLICATA (SHUMARD): LUGUBRIS (CONRAD) (SEE EXPLANATION OF PLATES AT END OF TEXT.)
