Crotalocephalus vs. Crotalocephalina

[jkbrower]

What is the relationship between Crotalocephalus and Crotalocephalina? After poking around on the web it seems that some treat these as synonyms, others (like the PBDB) seem to list them as separate genera, while still others indicate that crotalocephalus was renamed crotalocephalina (and then, according to fossilmuseum.net was in turn renamed Cheirurus). What's the real story? Or should I just call them all trilobites and be done with it?

[sdsnl]

They used to be the same genus (Crotalocephalus), but after more research, scientists decided to separate them into two genera, Crotalocephalus and Crotalocephalina. When a website writes something as Crotalocephalina (Crotalocephalus), it means the trilobite in question is now Crotalocephalina but used to be called Crotalocephalus. That is to avoid confusion for people who only know of the old name.

[jkbrower]

That makes a lot of sense. Thanks for the education.

[piranha]

They are two distinct genera described from various worldwide localities.

The four valid species from Morocco are listed below from Basse 2012.

 

 

Basse, M. (2012)
Trilobites Africae: Catalogus typorum. 
Fossilium Catalogus I: Animalia, 150:1-311

 

Crotalocephalina PŘIBYL & VANĔK, 1964

 

Cheirurus (Crotalocephalina) gibbus auster ALBERTI, 1970: Holotypus : CRAN, Nr. TA 307 (Service de la Carte géologique du Maroc, Rabat), ebd.: Taf. 10 Fig. 6a–c; SCHRAUT 2000a: Taf. 2 Fig. 3a–b (= Kopien) - Locus typicus : Fundpunkt 2 (TERMIER, TERMIER & COLO 1951), Aufschluss an der alten Piste von Tedders nach Oulmès (am Jbel Megrane), Marokkanische Meseta - Stratum typicum: Kalkknollenhorizont der Megrane-Schichten, Nowakia (Turkestanella) acuaria-Zone der Tentaculitenchronologie, Pragium.

 

Cheirurus (Crotalocephalina) gibbus tifletensis ALBERTI, 1981a: Holotypus: CRAN, unnummeriert oder Katalognummer nicht vermittelt, leg. DESTOMBES (Service de la Carte géologique du Maroc, Rabat), ALBERTI 1969: Taf. 38 Fig. 3a–d; SCHRAUT 1998a: Taf. 1 Fig. 12 (= Kopie der Fig. 3a); SCHRAUT 2000a: Taf. 2 Fig. 2a–b (= Kopien der Fig. 3a, d) - Locus typicus : Aïn ed Drou bei Tiflet, Rabat-/Tiflet-Gebiet, Marokkanische Meseta - Stratum typicum: Grauer Kalk, Nowakia (Turkestanella) acuaria- oder Guerichina strangulata-Zone der Tentaculitenchronologie, Pragium.

 

 

Crotalocephalus SALTER, 1853

 

Cheirurus (Crotalocephalus) maurus ALBERTI, 1966a: Holotypus (monotypisch): PYG ohne die vorderen zwei Randanhänge der rechten Seite, SMF 23016 (Senckenberg Forschungsinstitut, Frankfurt am Main), ebd.: Taf. 14 Fig. 5a–b; ALBERTI 1969: Taf. 38 Fig. 9 - Locus typicus : Profil RT VII/8, Ghtira-Tal, Rabat-/Tiflet-Gebiet, Marokkanische Meseta - Stratum typicum: Basaler „Princeps-Kalk“ (= Äquivalent eines tieferen Teils des Grou-Kalks), Nowakia (Turkestanella) acuaria-Zone der Tentaculitenchronologie, Pragium.

Cheirurus (Crotalocephalus) affinis meridianus ALBERTI, 1969: Holotypus (monotypisch): CRAN, Nr. TA 201 (Service de la Carte géologique du Maroc, Rabat), ebd.: Taf. 37 Fig. 1a–c - Locus typicus : Straßenanschnitt circa 1 km südöstlich vom Zentrum von Ezzhiliga, Marokkanische Meseta - Stratum typicum: Kalkknollen in Schiefern, Paranowakia geinitziana-Zone der Tentaculitenchronologie, Unter-Pragium (aktuelle Stratigrafie nach ALBERTI 1983: 38).

[sdsnl]

Right, they were further merged into Cheirurus...

[jkbrower]

Wait, merged?

 

Does this mean (1) everything that was once known as Crotalocephalus or Crotalocephalina is now known as Cheirurus, or (2) some species are still known as Crotalocephalus, others are known as Crotalocephalina (but were once known as Crotalocephalus), and still others are known as Cheirurus (but were once known as Crotalocephalus or Crotalocephalina).

 

The PBDB seems to indicate no. 2, listing all three as genera of family Cheiruridae.

 

This isn't rocket science. It's harder. My head hurts.

[doushantuo]

you've discovered the joys of taxonomy

[piranha]

On 9/9/2016 at 2:34 AM, sdsnl said:

Right, they were further merged into Cheirurus...

 

 

They were not merged into Cheirurus.  They were classified as subgenera of Cheirurus by Salter 1853 and Přibyl & Vaněk 1964:

 

 

Salter, J.W. 1853

Figures and descriptions illustrative of British organic remains.

Memoirs of the Geological survey of the United Kingdom, 7(1):1-12

 

Přibyl, A., Vaněk, J. 1964
Some remarks to the classification of the genus Cheirurus Beyrich (Trilobita).
Časopis Národního Muzea, oddil přírodovědný, 133:93-95

[jkbrower]

Ah. So there is Cheirurus (genus), which contains both Crotalocephalus (subgenus) and Crotalocephalina (subgenus).

 

I can feel my brain getting bigger and stronger.

 

Dare I ask how to tell Crotalocephalus and Crotalocephalina apart? (Sorry, my German is not up to the task.)

[piranha]

On 9/9/2016 at 10:27 AM, jkbrower said:

...Dare I ask how to tell Crotalocephalus and Crotalocephalina apart? (Sorry, my German is not up to the task.)

 

 

The Google translation is not perfect, but shows some of the differences described by Přibyl & Vaněk 1964:

 

 

Crotalocephalus: A subgenus of Cheirurus, characterized by the axis (sag.) by combined glabellar lines of the front and middle pair, by longer genal spines and 2-3 pairs of very long and narrow tail spines. Hypostome subpentagonal, with a couple of middle oblique grooves and short posterolateral thorns that are sometimes missing.

 

Crotalocephalina: A subgenus of Cheirurus in particular by a transversely arched and oblong elliptical, laterally somewhat imprinted tank. The glabella is extended forward and overlaps, surmounted usually by the remaining glabellar furrows overlap the front and middle pair have to glabella an almost straight course (tr.). Genal spines usually short. Of the thorax consists of 11 ribs with simple axial rings. Pleurae short, of almost equal length (tr.) as the spindle rings (tr.). tail with three to four pairs wide, strip-shaped extended and curved back tail spines that the make continuation of fins on the tail flanks. The duplication of the ventral thorax part is narrower at the hull ribs (tr.), and a wider tail than in (Crotalocephalus) SALTER .; takes approximately 1/4 of the sag. tail length.