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BULLETIN OF THE GEOLOGICAL SOCIETY OF AMER ICA

VOL. 66. PP. 467-470. 2 PLS. A P R I L 1955

DISCOVERY OF SONORASPIS IN SOUTHERN CALIFORNIA

B Y ALEXANDER STOYANOW AND TAKEO SUSUKI

Genus Sonoraspis was erected b y the senior writer (Stoyanow, 1952, p. 50, PL 14, figs. 1-6) for the Midd le Cambr i an tri lobites f r o m Sonora, Mexico, which differ f rom Anoria Walco t t (1924, p . 54; 1925, p . 67) and Glos-sopleura Poulsen (1927, p . 268), under which generic names they h a d been originally listed (Stoyanow, 1942, p . 1263-1264), in hav ing eight instead of seven thoracic segments and in possessing mixed character is t ics of those two genera.

T h e discovery of Cambr i an tri lobites in Sonora led McICee (1947, p. 282) to pos tu la te an early Middle C a m b r i a n seaway f rom t h e Grand Canyon area to Sonora across sou th -western Arizona. Th i s view was based chiefly on the presence of Glossopleura in H a r q u a h a l a M o u n t a i n s south of the G r a n d Canyon . T h e above in te rpre ta t ion was opposed b y t he senior wri ter (Stoyanow, 1948, p. 323-324) who pointed o u t the absence of C a m b r i a n s t r a t a between the two regions, and especially the fac t t h a t in C a m b r i a n t ime sou thwes te rn Arizona was occupied by the P recambr i an massive, Al tar Head land (Stoyanow, 1942, p . 1264) of Maza t za l L a n d (Stoyanow, 1936, p . 462; cf. Cooper and Arellano, 1946, p . 608), which p robab ly extended sou thward in to Sonora. A westward Paleozoic por t a l in the Sonora basin was suggested.

A tri lobite of the Anoria-Glossopleura g roup b u t with eight thoracic segments , collected f rom the Middle Cambr i an s t r a t a in Bris tol Moun ta ins , sou thern California, was de-scribed as Balhyuriscus howelli var . lodensis b y Clark (1921, p. 6) b u t was no t f igured. L a t e r Resser (1928, p . 10, PL 3, fig. 9) i l lustrated Clark ' s t ype advancing i t to the s t a tu s of species, Dolichometopus? lodensis (Clark) , and also ment ioned eight thoracic segments . H o w -ever, in a more recent pape r Resser (1935, p . 29, 34) placed this species, as Glossopleura lodensis (Clark) , wi th o ther species possessing

only seven thoracic segments, as also did M a s o n (1935, p . 109, PL 15, fig. 11) while describing, as Anoria lodensis, a plesiotype of Clark ' s species collected in Marb le M o u n -tains. Like Anoria, Clark 's species has a macropleural fifth thoracic segment . T h e illus-t ra t ions of Resser and Mason do not allow the figuring of the number of thoracic segments (eight as by Clark, or seven as by Resser and Mason) in either of two types wi th any degree of assurance. Clark 's holotype was no t avail-able a t the t ime of this writing, b u t Mason ' s plesiotype, preserved in the Los Angeles M u s e u m , has been examined by the writers th rough the kindness of D r . G. P . Kanakoff . I t has seven thoracic segments with the fifth segment macropleural as in Anoria. Since the thoracic axis is completely destroyed in this specimen, it is impossible to establish the presence or absence of the axial tuberculat ion.

T h e possible presence of Sonoraspis in southern California, as suggested by Clark 's ment ion of eight thoracic segments, s t imulated a more detailed research in the Middle Cam-br ian s t r a t a of California. Th rough indefatig-able and sys temat ic field studies the junior writer eventual ly located Sonoraspis in Marb le M o u n t a i n s abou t 50 feet below the base of Bonanza King format ion. Like 5 . torresi and 5 . gomezi of Sonora, it has, besides the presence of eight thoracic segments of the generic diag-nosis, and like those two species, certain mixed character is t ics of Anoria and Glossopleura. Sonoraspis califomica, sp. nov., has tubercles on the anterior thoracic segments and the course of the facial sutures as in Anoria, b u t like Glossopleura i t lacks the macropleural en-la rgement of the fifth thoracic segment. If Clark 's species f rom Bristol Moun ta ins has eight segments in the thorax, it is distinguished by the presence of the la t ter characteristic. T h e diagnostic description of the new species is presented below.

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467

468 S T O Y A N O W A N D SUSUKI—SONORASPIS I N S O U T H E R N C A L I F O R N I A

Sonoraspis califomica, sp. nov .

(Plate 1, figures 1 and 2)

This species has eight thoracic segments (none macropleural) as in the genotype, S. torresi (untuberculated thoracic segments and facial sutures as in Anoria), and as in S. gomezi ( tuberculated thoracic segments and facial sutures as in Glossopleura) f rom Sonora. I t differs f rom the first species in having tu-bercles on the thoracic segments and f rom the second by the Anoria-Wkt course of the facial sutures which is as in S. torresi. I t is f u r the r dist inct f rom S. gomezi by the presence of tubercles in the anterior segments of the thorax.

I n holotype the tubercles of two posterior segments are destroyed, b u t the pa ra type , al-though with a damaged median line, clearly shows t h a t all thoracic segments were tuber -culated, as in Anoria.

Diagnost ic differences: f rom Anoria and Glossopleura, by eight thoracic segments ; f rom S. torresi, by the thoracic tubercula t ion; f rom 5 . gomezi, b y the course of facial sutures .

T y p e : Holo type : U.C.L.A. Pa l . Coll., Ca t . No. 23460; P a r a t y p e : U.C.L.A. Pal . Coll., Ca t . No. 23461.

Occurrence: In bedded buff to yellow lime-stone, Cadiz format ion, 50 feet below the base of Bonanza King format ion , M a r b l e M o u n -tains, San Bernardino County .

T h e paleogeographic significance of the de-scribed find is as follows. T h e presence of either Anoria or Glossopleura in Sonora has no t been established. T h e four figured specimens f rom the Cambrian of Sonora wi th the thorax of eight segments preserved, o ther than those described by the senior writer , which were dis-cussed under Glossopleura by Lochman (1952, p . 137, PI. 31, figs. 8, 9, 12, 14), all belong in Sonoraspis. There is no t a single thorax illus-t ra ted or mentioned in the text within the

assemblage of cranidia and pygidia described by Lochman (1952, p . 135, PL 25, figs. 1-21) as Glossopleura leona. All these specimens m a y as well belong in SonoraspisThe logical con-clusion might be t h a t the Sonoraspis f a u n a was endemic to the Sonora basin, b u t the find in Marb le Mounta ins described here clearly indicates intermigrat ion with southern Cali-fornia. N o eight-segmented forms of the Anoria-Glossopleura group have been repor ted f rom the Cambr ian of the Grand Canyon thus far , b u t along the main Cordilleran t rough such specimens appear to be present as seen f rom Walco t t ' s i l lustrated mater ia l f rom C a n a d a and (less certainly) f rom U t a h (Stoya-now, 1952, p. 50-51).

T h e Marb le Mounta ins , where the So-noraspis beds have been located, are in San Bernard ino Coun ty between Bars tow and Needles, abou t 2 miles nor theas t of Chambless on U. S. Highway 66, 90 miles east of Bars tow. This locality has been described twice. I n an earlier paper , Hazzard and Crickmay (1933, p . 60, 64, 65, 68) placed in the Middle Cambr ian abou t 370 feet of s t r a t a between the topmos t Lower Cambr ian layer with Mesonacidae and the gray massive and bedded limestone com-plex above which was tenta t ive ly interpreted as Goodspring format ion. T h e index fossil collected in the upper 105 feet of the Middle Cambr ian , thus defined, was identified as Dolichometopus productus (H. and W.) . I n the second paper (Hazzard and Mason , 1936, p . 232, 233) the combined Middle Cambr ian sequence of Providence and Marb le M o u n -tains was termed Cadiz format ion , whereas the t en ta t ive Goodspring format ion was changed to Bonanza King format ion and added to the Middle Cambr ian as also t en ta -tively was the overlying Cornfield Spring format ion . T h e f auna from the upper 105 feet of Cadiz format ion was identified and l isted. A collection f rom Marb le Moun ta ins was de-scribed b y Mason (1935). T h e Cadiz f auna , as

PLATE 1—SONORASPIS CALIFORNICA, N . S P . A N D C O L L E C T I N G G R O U N D S

FIGURE 1.—HOLOTYPE. U . C . L . A . PAL. COLL., CAT. N O . 2 3 4 6 0 . X 1 .8

FIGURE 2.—PARATYPE. U . C . L . A . PAL. COLL., CAT. N O . 2 3 4 6 1 . X 2 .1

FIGURE 3 . — G E N E R A L VIEW o r MARBLE MOUNTAINS FROM U . S . HIGHWAY 6 6

FIGURE 4 . — W E S T E R N PART o r MARBLE MOUNTAINS

BULL. GEOL. SOC. AM., VOL. 66 STOYANOW AND SUSUKI, PL. 1

FIGURE 4

SONORASPIS CALIFORNICA, N. SP., A N D COLLECTING GROUNDS

BULL. GEOL. SOC. AM., VOL. 66 STOYANOW AND SUSUKI, PL. 2

FIGURE 1

FIGURE 2

STATUTE MILES

listed, appare horizons.

I t is safe 1 Sonoraspis in tively within Sonora, whic noraspis in t] this trilobite of Arellanella Arellano, 195 is indicated ; bend of the 1 3 of the same

T h e recent the appraisal f rom Great E af ter the pre for publicati Sonoraspis re<

"Sonoraspis preserved mat by having 8 ii writer does nol for generic dis knowledge ava

>7 feature within : sidered here t< K. ^ T h e presen Jv. the quali tat i ^ trilobites by ^ .qualitative- ft ^ generic and

Walcot t ian 1 noraspis was tional thorac

^ c o ^ i i n g l i n g o longing to A no such comb for the above any paleontol

FIGUR

V I E W S O F C O L L E C T I N G L O C A L I T Y Arrow

SHORT NOTES 469

listed, appa ren t ly represents several individual horizons.

I t is safe to conclude t h a t the s t r a t a wi th Sonoraspis in M a r b l e M o u n t a i n s are c o r r e c -t ively wi thin 500 feet of Arrojos fo rmat ion in Sonora, which is the vert ical range of So-noraspis in t h a t format ion , and wi thin which this t r i lobite genus occurs be tween the zones of Arellanella and Zacanthoides ( c f . Cooper and Arellano, 1952, p . 6; location of Arrojos Hills is indicated as " 8 0 0 " south of the sou thern bend of the R io Magda lena , see m a p on page 3 of the same publ icat ion) .

ADDENDUM

T h e recent paper of A. R . Pa lmer (1954) on the appraisa l of Middle C a m b r i a n tr i lobites f r o m G r e a t Bas in was received b y the wri ters a f te r the p resen t article h a d been submi t t ed for publ ica t ion . Pa lmer ' s t ex t concerning Sonoraspis reads (p. 67):

"Sonoraspis (Stoyanow, 1952) is based on poorly preserved material that differs from Glossopleura by having 8 instead of 7 thoracic segments. The writer does not consider this sufficient justification for generic distinction, especially with inadequate

fy knowledge available concerning variation of this feature within a population. Sonoraspis is con-sidered here to be a synonym of Glossopleura.

T h e presen t wri ters are of opinion t h a t : (1) ^ the qua l i t a t ive characteris t ics of C a m b r i a n ^ tr i lobites b y fa r outweigh in significance the ^ jjUKtlitative fea tures (so profuse ly used for ^ g e n e r i c a n d specific diagnoses in the pos t -

Walco t t i an l i t e ra tu re ) ; (2) the genus So-noraspis was erected no t only on the addi -t ional thoracic segment , b u t also on the

j y ^ co^iingling of characteris t ics separa te ly be-longing to Anoria and Glossopleura, whereas no such combinat ions have been demons t r a t ed for the above genera ; (3) the pr incipal task of any paleontologist is in the appl icat ion of his

ability to derive correct interpretation from impaired materials, and deductions made by the senior writer from the less perfect Sonora material have been corroborated by the ex-cellent specimens from'California; (4) there is a considerable range of intrageneric variations (including spinosity) in Sonoraspis, but the eighth thoracic segment invariably is present.

REFERENCES CITED

Clark, C. W., 1921, Lower and Middle Cambrian formations of the Mohave Desert: Univ. Calif., Dept. Geol. Sci. Bull., v. 13, p. 1-7.

Cooper, G. A., and Arellano, A. R. V., 1946, Stratig-raphy near Caborca, northwest Sonora, Mexico: Am. Assoc. Petroleum Geologists Bull., v. 30, p. 606-611.

1952, Introduction and stratigraphy in Cam-brian stratigraphy and paleontology near Caborca, northwestern Sonora, Mexico: Smith-son. Misc. Coll., v. 119, no. 1, p. 1-23, Pis. 1-5.

Hazzard, John C., and Crickmay, Colin H., 1933, Notes on the Cambrian rocks of the eastern Mohave Desert, California: Univ. Calif., Dept. Geol., Bull., v. 23, no. 2, p. 57-78, PL. 1.

Hazzard, John C., and Mason, John F., 1936, Middle Cambrian formations of the Providence and Marble Mountains, California: Geol. Soc. America Bull., v. 47, p. 229-240.

Lochman, Christina, 1952, Trilobites in Cambrian stratigraphy and paleontology near Caborca, northwestern Sonora, Mexico: Smithson. Misc. Coll., v. 119, no. 1, p. 60-161, Pis. 18-31.

Mason, John F., 1935, Fauna of the Cambrian Cadiz formation, Marble Mountains, Cali-fornia: Southern Calif. Acad. Sci. Bull., v. 34, pt. 2, p. 97-119, PI. 15.

McKee, E. D., 1947, Paleozoic seaways in western Arizona: Am. Assoc. Petroleum Geologists Bull., v. 31, p. 282-292.

Palmer, Allison R., 1954, An appraisal of the Great Basin Middle Cambrian trilobites described before 1900: U. S. Geol. Survey Prof. Paper 264-D, p. 55-86, Pis. 13-17.

Poulsen, Chr., 1927, The Cambrian, Ozarkian and Canadian faunas of northwest Greenland: Meddelelser om Gr^nland, v. 70, p. 233-343, Pis. 14-21.

Resser, Charles E., 1928, Cambrian fossils from the Mohave Desert: Smithson. Misc. Coll., v. 81, no. 2, p. 1-14, Pis. 1-3. , 1935, Nomenclature of some Cambrian trilo-

PLATE 2 . — V I E W S O F C O L L E C T I N G L O C A L I T Y

FIGURE 1.—COLLECTING GROUNDS, MARBLE MOUNTAINS, SAN BERNARDINO COUNTY,

CALIFORNIA

T—indicates the trail

FIGURE 2.—CLOSE VIEW OF COLLECTING'LOCALITY

Arrow indicates Sonoraspis beds. B—marks the basal part of Bonanza King formation.

FIGURE 3.—ORIENTATION M A P

470 STOYANOW AND SUSUKI—SONORASPIS IN SOUTHERN CALIFORNIA

bites: Smithson. Misc. Coll., v. 93, no. 5, p. 1-46.

Stoyanow, Alexander, 1936, Correlation of Arizona Paleozoic formations: Geol. Soc. America Bull., v. 47, p. 459-540, PI. 1.

1942, Paleozoic paleogeography of Arizona: Geol. Soc. America Bull., v. 53, p. 1255-1282, Pis. 1-5.

1948, Some problems of Mississippian stratig-raphy in southwestern United States: Jour. Geology, v. 56, p. 313-326.

1952, The original collection of Cambrian trilobites from Sonora in Cambrian stratig-

raphy and paleontology near Caborca, north-western Sonora, Mexico: Smithson. Misc. Coll., v. 119, no. 1, p. 49-59, PI. 14.

Walcott, Charles D., 1924, Cambrian geology and paleontology. Cambrian and Ozarkian trilo-bites: Smithson. Misc. Coll., v. 75, no. 2, p. 53-60, Pis. 9-14.

1925, Cambrian geology and paleontology. Cambrian and Ozarkian trilobites: Smithson. Misc. Coll., v. 75, no. 3, p. 61-146, pis. 15-24.

UNIVERSITY OF ARIZONA, TUCSON, ARIZ.; UNIVER-SITY OF CALIFORNIA, L o s ANGELES, CALIF.