Spondylus subnodosus (Packard, 1922)
PACKARD, E. L. 1922. New species from the Cretaceous of the Santa Ana Mountains, California. University of California Publications, Bulletin of the Department of Geological Sciences, 13 (10): 413-462, pls. 24-38. [p. 421, pl. 28]
1922 Lima subnodosa Packard, 1922
1922 Spondylus striatus Packard, 1922
1922 Spondylus fucatus G. D. Hanna, 1924
1922 Spondylus striatus Packard, 1922
1922 Spondylus fucatus G. D. Hanna, 1924
E. L. Packard, 1922, plate 28.
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«Type specimen 12275, Coll. Invert. Palae., Univ. Calif., Ioc. 2149.
Shell very large, nearly equivalve; anterior dorsal margin sloping in a straight line from the beaks to a point about midway from the beaks to the base. Anterior end evenly rounded; base arcuate; posterior dorsal rnargin apparently curves convexely from the small beak toward the posterior extrernity, which appears to be broken. Anterior ear long, the dorsal margin sloping slightly; posterior ear broken. Surface of the valve ornamented by numerous fine ribs becoming obscured toward the base by radial rows of nodes on some of the stronger ribs. These nodes extend from 3 to 5 millimeters above the surface from which they rise. Length of type, 140 mm.; height, 150 mm.; convexity, 30 mm. Horizon.— Chico group, zonal position uncertain.»
EARL LEROY PACKARD, 1922
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«Spondylus subnodosus is a common faunal element in the oyster-rich beds. It is represented by numerous shells and molds. This species is characterized by large, inequivalve shells (specimens up to 100 mm high and 70 mm wide) having numerous radiating, flat-topped ribs. On some specimens, every fifth to seventh rib is more strongly developed and has small nodes. The radials are evident on the internal surfaces of small- to medium-sized specimens, becoming visible only on the peripheral regions of large shells. Broad rugae are present on the one right valve collected at Lorna Prieta, and narrow, sharp rugae are present on the periphery of large left valves. Packard (1922) described this species as both Spondylus striatus Packard, 1922 and Lima subnodosa Packard, 1922 (see Packard (1922) for further description). Hanna (1924) pointed out that S. striatus Packard is a junior homonym but apparently failed to recognize L. subnodosa as a synonym for the above and replaced S. striatus Packard with S. fucatus Hanna, 1924. In accord with the International Code of Zoological Nomenclature (1985, article 60b), the name S. subnodosus is adopted for this species, and S. fucatus Hanna, 1924 becomes a junior synonym.
In addition to the Santa Ana Mountains where the type locality of Spondylus subnodosus is found, it has been recorded from near San Diego (Sundberg, 1984; Sundberg and Riney, 1984). Spondylus probably attributable to this species also have been found in rocks of the lower Maastrichtian Rosario Formation in Baja California (Anderson and Hanna, 1935; Anderson, 1958). Spondylus fragments are rare elements in several Menlo Park USGS collections from Campanian rocks of the San Joaquin Valley. Spondylus are cementing epifaunal bivalves that attach to hard substrates by their larger right valves. Cretaceous as well as modern Spondylus typify high-energy wave- or current-dominated environments, as their occurrence in the Cretaceous on the upper surfaces of boulders on a rocky coast and on reef tops illustrates (Surlyk and Christensen, 1974). The much greater number of left valves relative to right valves found at Lorna Prieta suggests that the more robust right valves tended to remain cemented to near-shore rocks after death, whereas the left valves became detached after breakdown of the ligaments and were transported offshore and downslope by turbidity currents.» ELDER, W. P. 1991. An Unusual Late Cretaceous Fauna from an Oyster-Rich Interval in the Santa Cruz Mountains of California. Shorter Contributions to Paleontology and Stratigraphy, United States Geological Survey Bulletin, 1934 (E): 1-18, pls. 1-5. [p. 10]
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Spondylus subnodosus (Packard), 1922; W. P. Elder, 1991, An Unusual Late Cretaceous Fauna from an Oyster-Rich Interval in the Santa Cruz Mountains of California, plate 2, figures 1-4; plare 3, figures 8, 13.
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