THE SYSTEMATIC POSITION OF THE SURFBIRD, APHRIZA VIRGATA JOSEPH R. JEHL, JR. University of Michigan Museum of Zoology Ann Arbor, Michigan 48104 The taxonomic relationships of the Surfbird, ( 1884) elevated the tumstone-Surfbird unit Aphriza virgata, have long been one of the to family rank. But, although they stated (p. most controversial problems in shorebird clas- 126) that Aphrizu “agrees very closely” with sification. Although the species has been as- Arenaria, the only points of similarity men- signed to a monotypic family (Shufeldt 1888; tioned were “robust feet, without trace of web Ridgway 1919), most modern workers agree between toes, the well formed hind toe, and that it should be placed with the turnstones the strong claws; the toes with a lateral margin ( Arenaria spp. ) in the subfamily Arenariinae, forming a broad flat under surface.” These even though they have reached no consensuson differences are hardly sufficient to support the affinities of this subfamily. For example, familial differentiation, or even to suggest Lowe ( 1931), Peters ( 1934), Storer ( 1960), close generic relationship. and Wetmore (1965a) include the Arenariinae Coues (1884605) was uncertain about the in the Scolopacidae (sandpipers), whereas Surfbirds’ relationships. He called it “a re- Wetmore (1951) and the American Ornithol- markable isolated form, perhaps a plover and ogists ’ Union (1957) place it in the Charadri- connecting this family with the next [Haema- idae (plovers). The reasons for these diverg- topodidae] by close relationships with Strep- ent views have never been stated. However, it silas [Armaria], but with the hind toe as well seems that those assigning the Arenariinae to developed as usual in Sandpipers, and general the Charadriidae have relied heavily on their appearance rather sandpiper-like than plover- views of tumstone relationships, because schol- like. Aphriza might go under Haematopodi- ars who have paid particular attention to the dae next to Strepsilas [he considered the turn- Surfbird alone have concluded (1) that it is stones a subfamily of the oystercatchers] or, closely related to the Scolopacidae’ (Shufeldt perhaps better, Aphriza and Strep&m might 1888), (2) that it is an offshoot of the sub- together constitute a family Aphrizidae, next to, family Calidridinae* (Lowe 1931)) or (3) that but apart from, Haematopodidae.” Although there is no evidence against its inclusion in he adopted the latter course ( 1903), his result- the Scolopacidae (Bock 1958). In this paper ing classification was one of convenience, since I wish to review and extend the evidence that he stated (p. 783) “there is probably no better supports the inclusion of the Surfbird in the way of arranging these two unconformable Scolopacidae. genera.” Coues also thought these genera had “much in common,” but noted only (p. 784) HISTORY OF SURFBIRD TAXONOMY that they “agree in structure of feet, which are Described as Tringa virgutu by Gmelin in 4-toed, with anterior toes cleft to base and 1789, the Surfbird was placed in a new genus, tarsi scutellate in front.” By these criteria the Aphriza, by Audubon ( 1839 ) , who took no Aphrizidae has much in common with many definite stand on its relationships. Yet, he did families. note (p. 249) that it bore “a considerable re- Shufeldt (1888) made the first serious at- semblance to the Knot” as well as to the turn- tempt to determine the Surfbirds’ relationships stones, and that it differed from the latter in by comparing its skeleton with those of other bill morphology, tail shape, and tarsal scutel- Charadrii, including Arenuriu, Chad&q and lation. Sclater and Salvin ( 1873:143), without Haematopus. He concluded (p. 337) that the stated reasons, united the Surfbird, turnstones, “sum total of skeletal characteristics place . and Pluvi~ndlus sociulis as a subfamily of the [Aphriza] nearer the Tringeae [ Scolopacidae] Charadriidae. Baird, Brewer, and Ridgway . * . than it does to the plovers; less to Arenaria, and far less to Haematopm.” He placed * The name of this subfamily has been spelled “Cali- Aphriza and Arena&z in separate families. dridiinae” (e.g., A.O.U. 1957) and Calidritinae (e.g., Ridgway (1919:57), who followed Shufeldt, Lowe 1931). According to Brown ( 1954: 724) the genitive singular of the feminine Greek word skalidris characterized these families as follows: (ca1idri.sL.) is skaltiridos. Thus, the stem of the a. Bill distinctly convex terminally and constricted word is skalidrid-, and the name of the subfamily subterminally, neither the maxilla nor man- should become Calidridinae. dible depressed terminally; lateral grooves of TheCondor, 70:206-210, 1968 f2061 SYSTEMATIC POSITION OF THE SURFBIRD 207 bill extending to base of convex terminal por- ment of the Arenariinae. It seems obvious tion; legs and feet much more robust, the lat- from the foregoing review that the cause of eral membrane of anterior toes more strongly this disagreement is the tacit assumption that developed, distinctly roughened or serrate; transverse scutella of acrotarsium broken into Aphrixa is most closely related to Arenuria hexagonal scales on upper and lower portions; and, therefore, that both genera must be clas- planta tarsi reticulate; tail emarginate sified together. A consideration of the rela- __.._____.._.______.-.----_.-.__-------...-..--..---.-.-...-.Aphrizidae. tionships of the turnstones is beyond the scope aa. Bill tapering to the acute tip, not constricted of this paper, but it must be emphasized that subterminally, both maxilla and mandible flat- tened at tip; lateral grooves of bill extending no evidence yet offered strongly supports the not more than half way to tip; legs and feet Arenariinae as a natural taxon. more slender, the lateral margin of anterior toes less developed, smoother; transverse scu- RELATIONSHIP OF THE SURFBIRD tella of acrotarsium continuous; planta tarsi TO THE CALIDRIDINE SANDPIPERS scutellate; tail truncate . Arenariidae. Lowe ( 1931:747-50) not only claimed that Note that the differences that Ridgway used the Surfbird was a sandpiper, but he also to separate these families include character- postulated that it was most closely related to istics of foot structure that Baird, Brewer, and the Knot (Calidris can&us) and the Red- Ridgway (1884) and Coues (1884; 1903) had backed Sandpiper (Erolia alpina). Skull previously used to unite Aphriza and Arena& morphology provided the major support for in a single family. his position. Other evidence further indicates From studies of myology, pterylography, the Surfbirds’ affinity to the calidridine sand- color pattern, and skull morphology, Lowe pipers, and particularly to the Knot and the ( 1931: 747-50) concluded that Arena& and Great Knot (C. tenuirostris). Aphrixa were closely related, and that both were specialized calidridine sandpipers. How- EXTERNAL MORPHOLOGY ever, his myologic and pterylographic studies In a separate study (Jehl 1967) it was shown were inconclusive, and merely showed that that downy plumages offer a highly reliable both forms were waders. Furthermore, his index to relationships in the waders (Suborder remark (p. 749) that “the colour-pattern of Charadrii). The Surfbird chick is typically Aphriza and Arenariu present points of such calidridine in color, pattern, and feather struc- obvious resemblance that . it can hardly ture, and is completely distinct from chicks of fail to suggest a genetic basis of community” turnstones, plovers, or other groups of waders. was clearly an overstatement. The only “ob- An excellent photograph of newly hatched vious” resemblance is between the nonbreed- Surfbirds may be found in Wetmore ( 1965b: ing plumages of the Surfbird and Black Tum- 324). The only specimen known to me (U.S. stone (Arena& melunocephulu) , and this may Natl. Mus. no. 286741; description in Bent be due to convergence, since both species in- 1929:273) is of a chick approximately one habit rocky coasts in winter (cf. also the rather week old, in which the primaries, scapulars, similar nonbreeding plumages of other rock- and some of the flank feathers had begun to inhabiting waders, e.g., Eroliu muritimu, E. erupt. This chick is shown with chicks of ptilocnemis, Heteroscelus incanus, and Hae- Calidris canutus and Arena&z interpres in fig- matopus bachmuni) . Skull morphology did ure 1. Although it is not evident in the photo- support his view. He showed (1925) that the graph, owing to the age of the chick and the morphology of the quadrate was useful in preparation of the skin, the Surfbird chick is distinguishing sandpipers from plovers, and nearly identical to that of the Knot, even to ( 1931) that the structure of the maxillo-pala- details of face pattern; moreover, it is more tine strut could be used to separate the major similar to Knot chicks than to those of other scolopacidine groups. In Aphriza and Are- calidridine sandpipers. Portenkos’ plate ( 1933: n&a “the quadrato-tympanic morphology . , opp. p. 96) shows that chicks of the Great is scolopacidine” and “the morphology of the Knot are like those of the Knot. The turnstone maxillary-palatine angle is . eroliine” (Lowe downy plumage is not calidridine, but has 1931: 748 ) . probably been derived from that of the tringine Bock (1958:86) confirmed that the palate sandpipers (Jehl 1967). structure in these genera was like that of the The breeding plumage of the Surfbird, calidridine sandpipers; yet, he considered the which is totally unlike that of the plovers and Arenariinae “Incertae Sedis.” turnstones, is similar to that of several cali- In summary, although the only substantial dridine sandpipers, but most closely resembles evidence that has been presented to date indi- that of the Great Knot. The pattern and color- cates that Aphrixa, at least, is a sandpiper, ation on the head, neck, and back of these taxonomists continue to disagree on the place- species are nearly identical. The heart-shaped 208 JOSEPH R. JEHL, JR. FIGURE 3. Ventral view of Aphriza uirgccta (left) and C&u!& tenuirostris (right) in breeding plumage. Aphriza is scutellate to reticulate anteriorly, FIGURE 1.