According to Compagno (2001: 69-70) the extant species is a poorly known (Atlantic & Pacific) bottom dweller of the outer continental shelf (to over 1000 meters). It is a medium-sized shark (to 3.5 - 4.0 m) with a bizarre appearance -- long caudal fin, "flabby" body and greatly elongated, dorsoventrally compressed, blade-like snout. Notable characteristics include its long-cusped anterior teeth and protrusible jaws. Greater detail on the Mitsukurina dentition can be found in the accompanying slideshow.
Briefly however, the anterior hollows (sensu Siverson 1999) contain long awl-like teeth (3 upper & 4 lower¹) while the laterals are shorter with strongly splayed roots. Teeth from the lower lateral hollow are more lingually curved than the uppers which have a labial recurvature of the cusp tip -- primarily a clutching/grasping design.

Fossil record

Cappetta & Case (1975: 14) limited two fossil genera (based on tooth-design) to this family, Scapanorhynchus and Anomotodon. Complete skeletons of Scapanorhynchus lewisii (with paddlefish-like rostrums) are known from Lebanon (Cappetta 1980), and that species appears to be very similar to the extant goblin shark Mitsukurina owstoni.²
The published fossil record for this tooth-design is extensive and multiple species have been erected and attributed to it; some of which are quite dubious. When erecting Scapanorhynchus perssoni, Siverson (1992: 541) only deemed three others as having well defined tooth groups: S. texanus, S. lewisii and S. rapax.. In that paper he questioned S. kysylkumensis as being too similar to S. raphiodon (AGASIZ, 1843³, sensu Herman 1977) yet did not consider S. raphiodon a valid taxon⁴. In follow-up discussions with Siverson (pers com. 2008), he had now accepted five valid species for inclusion in Scapanorhynchus:

Roemer's (1849) ⁵ Lamna texana from the Late Cretaceous of Texas⁶;

Davis' (1887) Rhinognathus lewisii from the Late Santonian of Lebanon;

Quaas' (1902) Scapanorhynchus rapax from the Cretaceous of Egypt;

Sokolov's (1978) S. kysylkumensis and

Siverson's (1992) S. perssoni of the Campanian of Sweden. Siverson's comment only includes fully described tooth-designs, using valid names, not previously described and corresponding with type material. Because the published record contains many references to S. raphiodon (nomen dubium as footnoted) it will be referred to as S. "raphiodon" on the website; NA Western Interior Seaway (WIS) tooth-designs ascribed to this bucket may not correlate with those from the Tethys.

North American reports

Early reports of the Scapanorhynchus tooth-design include Morton (1834, 35), Roemer (1849), Gibbes (1849) and Emmons (1856). This is a complex history further muddled by Williston (1900) interpreting all NA Scapanorhynchus teeth as S. raphiodon; and Meyer (1974) looking to basal labial folds to differentiate S. ?raphion from S. ?texanus. The pre-1995 NA publications and those S. texanus-centric will be included in the Scapanorhynchus II page; some relevant items might be included on both.
East & Gulf coasts. Cappetta & Case (1975a, Campanian, NJ) was the first to well-document in text and images, S. texanus. Reports along the East Coast (largely Campanian) have tended to follow these determinations. The Gulf region was more highly influenced by Meyer (1974) and placed Santonian texanus-like teeth in raphiodon.
Western Interior Seaway studies (Turonian-Santonian) largely report S. "raphiodon" although Gibbes (1849)'s "Lamna contortidens" appears to be the earliest report of S. texanus from the WIS. These western sediments often include much older horizons than seen on the East Coast and specimens are attributed to Scapanorhynchus "raphiodon". More recent studies include:

Stewart (1990: 21) S. raphiodon Green Horn Ls, Carlile Sh, & Smoky Hill Chalk (Turonian-Santonian), KS;

Shimada (1996: 6) S. sp., Ft Hays Ls, Niobrara Chalk (lwr/mid Coniacian), KS; and

Hamm & Shimada (2002) S raphiodon (5 assoc. teeth) Niobrara Fm, (?Santonian), KS.
None of these reports provide a useful suite of figures to document the basis for their determinations.

Bourdon et al (2011:17-27) document teeth interpreted as Scapanorhynchus from the Santonian of New Mexico; included are three tooth designs, none of which compare well with S. raphiodon (sensu Herman, 1977) or the S. "raphiodon" of the WIS. These include:
    - S. puercoensis BOURDON et al, 2011;
    - S. cf. tenuis (CASE et al., 2001); and
    - S. cf. texanus (ROEMER, 1849).
Texas provides an excellent Cretaceous marine fossil record which has been studied extensively over the years.

Meyer's (1974: 231-37) earliest report of S. ? raphiodon was from the Uppermost Woodbine Fm (Cenomanian); and latest, from the Austin Group (Lower Coniacian) of Texas. S. ?texanus ranged from the Tombigbee Sand (Santonian) of Mississippi through the Coffee Sand (Upper Campanian) of Mississippi.

Welton & Farish (1993: 94-95) include S. "raphiodon" as represented in Turonian-Coniacian sediments and S. texanus from the Campanian-Maastrichtian.

Case & Cappetta (1997: 142, pl 3.9, 4.1-3) include as Scapanorhynchus sp. small teeth from the Kemp Clay (Late Maastrichtian) of Texas (pl 3.9, 4.1-3). Plate 4 figs. 1 & 2 certainly appear to reflect Scapanorhynchus and do not compare well with texanus as 'defined' in Cappetta & Case (1975).

Cappetta & Case (1999: 19-21) included in the Texas fauna:     - S. texanus (Campanian) [no illustrations, these probably corresponded with their 1975 paper],
    - S. cf "raphiodon" (pl. 11.5-11, captioned as S. sp in the plates) Turonian-Coniacian (compare well with the Welton & Farish examples but less well with those in Herman 1977, plate VII),
    - S. aff praeraphiodon SOKOLOV 1978 (pl. 11.1-3) Upper Cenomanian and
    - Scapanorhynchus sp. (pl. 11.8) Lower Campanian.

Hamm & Cicimurri (2011: 113) included S. raphiodon in the Atco Formation (Early Coniacian) of Texas.

Dentition-design

S. lewisii. Cappetta (1980) studied and reported on the skeleton of Davis' R. lewisii from the Late Santonian of Lebanon. He determined:

Upper: 3 anteriors | 1(2) intermediates | 9-10 laterals | 8-11 posteriors

Lower: 1 symphyseal | 1 parasymph. | 2 anteriors | 8-10 laterals | 5 posteriors
The author's description of his first lower lateral (p 104) could very well represent the LA3 tooth-design in the above extant dentition. Positional terminology aside, Cappetta's overall formula corresponds very well with the extant dentitions above. Intermediates are sometimes present in Mitsukurina owstoni, however, not the lower symphyseal he describes (p 103). The website will view the dentition as made up of 3 upper (UA1-UA3) and four lower (LA0-LA3) anteriors. The exact number of large laterals likely varies based on species and possibly individual/sex as well; a refined number will require reconstruction for each species, but there were probably 8-10 uppers and one less lower. Posterior tooth counts most likely vary based on individual as well with six or more posterior files.

S. texanus. Based on studies of teeth from this taxon (Bourdon, 2008), this grasping-cutting dentition's hypothetical tooth formula would be:

Upper: 3 anteriors | 9 mesolaterals | 5-7 posterolaterals

Lower: 4 anteriors | 7 mesolaterals | 3 or more posterolaterals.
This study was not deemed definitive, however when compared with S. lewisii, it appears quite different.

Tooth-Design

Scapanorhynchus is best characterized by:

awl-like anteriors with a well-folded lingual face, high root lobes which may or may not have cusplets in the first two positions;

laterals with a smooth or folded lingual face, splayed root lobes, one or more cusplets;

upper laterals are inclined, more so distally;

lower laterals are more erect, growing lower distally; and

well-developed nutritive groove.

S. puercoensis BOURDON et al, 2011 was erected for a S. lewisii-like dentition-design from the Santonian of New Mexico. The authors primarily focused on the abundant small (9-14 mm) teeth of this design and speculated they may be young juveniles (Figs. - below). It is further characterized by:

all anteriors with one cusplet; laterals with pair, secondary reduced,

lingual cusp face strongly folded, both anteriors and laterals,

labial face is smooth, often bearing short parallel basal folds

intermediate tooth position(s) present,

neck lacks ridges and

root lobes are long, narrow and splayed to give the basal margin a V-shape.
S. lewisii has: longer anterior cusplets, only single lateral cusplets, uA3 with shorter mesial shoulder, likely more tooth positions and only known from deep offshore waters.
In addition to the smaller teeth, Bourdon et al (2011) reported several larger teeth as S. ?puercoensis speculating they may represent the adult form (Figs. - below).

S. raphiodon AGASSIZ (1843) is problematic. Is the name invalid as suggested by Siverson? There is certainly nothing diagnostic in Agassiz's specimen suite of A1 cusps (Fig. ). Even if the name were to be deemed valid, do the NA teeth equate with those from Western Europe? Herman (1977) provides a S. raphiodon specimen suite (Fig. ), but does it represent a single species? His specimen suite does not appear homogeneous; dentition-reconstruction might provide some answers.

S. "raphiodon" represents one or more undescribed species from the Cenomanian-Coniacian of Texas and the Western Interior Seaway. Welton & Farish (1993:94) examples do not appear to be homogeneous and some vary from those of Hamm & Shimada (2002). In the below image (Fig. a-f), the isolated tooth (Turonian) appears to have larger cusplets than the associated teeth.

S. tenuis (CASE et al 2001) was described as Microdontaspis tenuis from the Santonian of Georgia. These teeth are very similar to S. puercoensis, however: the upper anterior cusplets are more elongate, the ?UA2 doesn't correspond with any position in S. puercoensis, the UA3s are different and the lateral cusplets are more triangular. Case used nearly the smallest specimen as the type (similar to Fig. herein) but other specimens were larger. In addition, enlargement factors in their paper were not always correct. This taxon should not be confused with Scapanorhynchus tenuis DAVIS 1890 which had been moved to Odontaspis.

S. texanus ROEMER (1849) is the well known and documented tooth-design of upper Late Cretaceous sites (Sant.- E. Maas) of the Eastern US, Gulf Coast, Texas and extending to New Mexico (see S. texanus page). It is further characterized by:

anteriors that lacking cusplets in first position,

no intermediates,

lingual folds begin to disappear in the second lateral position,

the neck very often has ridges and

the lower labial face, short basal folds.

Acknowledgements

I need to thank, Mike Everhart & Shawn Hamm for images, Pieter DeSchutter & David Ward for modern literature, Mikael Siverson for his insight & comments and Earl Manning for obscure literature & observations on the topic.

Footnotes

1.	Some authors refer to a small tooth in the first position of the anterior hollow as a parasymphyseal. This website considers it an anterior and refers to it as an A0 when present.
2.	Case (1980: 81) argues that Scapanorhynchus has priority and the extant taxon should be included in Woodward's (1899) genus.
3	1844 is the normally cited date for S. raphiodon. Ward (pers. com. 2008) notes that the plate (37a) was published in 1844 while the text was 1843. Sherborn's Index Animalium as online at the Smithsonian notes it as: raphiodon, Odontaspis, J. L. R. Agassiz, Poiss. Foss., Feuilleton, 55 (1835) [n. n.]. Manning (pers. com. 2008) notes that Meyer (1974) cites Agassiz (1833-1843) and Woodward, 1911, p. 211, gives the citation as: "1843. Lamna (Odontaspis) raphiodon L. Agassiz, Poiss. Foss., vol. iii, p. 296, pl. xxxvii-a, figs. 12-16 (non fig. 11)." All things considered, this website will go with 1843.
4.	Siverson (pers com 2007): "Basically, in my view this nominal species [S. raphiodon] is based on indeterminable material, almost certainly including teeth (more precisely cusps) from more than one genus. It is therefore a nomen dubium as the name can only be applied with confidence to the syntypes. I challenge anyone who disagrees with me to please show me the diagnostic features of this nominal species. The stratigraphic origin of the syntypes is unknown so it is not possible to collect better preserved material from a type stratum. I don't even think a lectotype has been designated so there would not even be a (unknown) type stratum."
5.	The published literature yields two dates for S. texanus, 1849 and 1852. Manning (pers com. 2008) notes: "I take this to mean [the title] that this is a big book about Roemer's travels in Texas, probably a guidebook for German immigrants. I see something about a natural history appendix (naturwissenschaftlichen Anhange), and maps (Karte), but nothing about plates (Tafeln). The 100-page 1852 paper says prominently, in its subtitle, that it has 11 plates. For now, the website will follow the consensus citation 1849.
6.	Manning (pers com 2008) notes, "I had a look at his descriptions (pp. 29-31, in German, which makes it more difficult), and they're very professional, even starting with Latin descriptions. His text and synonymy-list citations are appropriate (Agassiz, 1843; Reuss, 1845; his own 1849 book; Dixon, 1850; - I give him extra credit for noting the similarity of his L. texana to Morton's 1834 pl. 11, fig. 2; and Reuss' Turonian "L. plicatella", now S. r. raphiodon). I'd guess he was taught paleontology very rigorously, in a strict German school, and that this is his own work. I might note that the source of all these fossils is "an der Furt der Guadalupe bei Neu-Braunfels." - at the ford of the Guadalupe River, near [likely just SE of] New Braunfels, between San Antonio and Austin, in SE Comal Co., south-central Texas. This is probably Campanian Taylor Grp. New Braunfels was an old German settlement in Texas. The faulting over the Balcones Escarpment (the edge of the E. Cret. limestones, where the Gulfian Gulf Coastal Plain starts) is so bad in this area, you'd never get the exact bed they come from (maybe from the ammonites). Actually, I'm sort of disappointed that Welton & Farish (1993, p. 45) didn't attempt to do this, it being a fine old Texas Cret. species. As I've said, I distrust their (and Case & Cappetta, 1997's) Maastr. Scapanorhynchus records."

Selected References