Exploring the limits of morphospace: Ontogeny and ecology of late Viséan ammonoids from the Tafilalt, Morocco Author Klug, Christian Author Baets, Kenneth De Author Korn, Dieter text Acta Palaeontologica Polonica 2016 2016-01-18 61 1 1 14 http://dx.doi.org/10.4202/app.00220.2015 journal article 10.4202/app.00220.2015 1732-2421 10626349 Goniatites lazarus Korn, Klug, and Mapes, 2005 Fig. 2−4 . Type material : Holotype GPIT 1851–97 ( Korn et al. 2005 : figs. 8.1, 8.2) ; paratypes MB.C. 5307 and MB.C. 5308 . Type locality : 12 km southeast of Dar Kaoua , southeast of Erfoud , eastern Anti –Atlas, Morocco . Type horizon : Early late Viséan ( Entogonites assemblage). Material .— 25 juveniles : 6 in PIMUZ 31508 , 1 in PIMUZ 31509 , 6 in PIMUZ 31510 , 2 in PIMUZ 31512 , 1 in PIMUZ 31520 , 2 in PIMUZ 31518 , 7 in PIMUZ 31519 . 4 ; adults: MB.C. 25130 , PIMUZ 31514–16 . Emended diagnosis (modified after Korn et al. 2005 ).— Goniatites with an extremely broad spindle-shaped juvenile conch (dm 1.1–6 mm ; ww/dm up to 1.76), later with a pachyconic conch up to 40 mm dm (ww/dm 0.70) and thickly discoidal conch at 70–100 mm diameter (ww/dm 0.6–1.00). Umbilicus almost closed (uw/dm 0.01–0.03) in all growth stages. Low aperture, moderate whorl expansion rate ( 1.7 in juvenile whorls, and nearly 2 near adulthood). The spindle-shaped juvenile whorls carry an umbilical ridge that vanishes at a diameter of about 7 mm . Suture line with V-shaped external lobe with slightly sinuous flanks, moderately high median saddle (one-third of the symmetric, narrowly rounded ventrolateral saddle). Shell ornament with crenulated growth lines with convex course in juvenile to adult whorls. Table 2. Measurements (in mm) and ratios of Goniatites lazarus . Abbreviations: ah, apertural height; D, the distance between the generating curve and the coiling axis; dm, diameter; S, the shape of the generating curve; uw, umbilical width; W, whorl expansion rate; WER, whorl expansion rate; ww, whorl width (measured between ribs).

Specimen	dm	ww	uw	ah	WER	ww/dm	ah/dm	uw/dm	W	D	S
PIMUZ 31514	97	61	1.2	17	1.47	0.63	0.17	0.01	1.40	0.08	1.20
6.04	8.5	0.4	1.26	1.56	1.41	0.21	0.07	1.53	0.08	2.67
PIMUZ 31510, section 1	4.82	7.38	0.32	1.14	1.61	1.53	0.24	0.07	0.08	3.13
3.8	6.23	0.28	0.75	1.74	1.64	0.20	0.07	0.05	2.84
5.31	7.1	0.35	0.99	1.56	1.34	0.19	0.07	1.57	0.14	3.06
4.25	6.69	0.2	0.78	1.55	1.57	0.18	0.05	0.10	3.04
PIMUZ 31510, section 2	3.41	4.7	0.7	1.60	1.38	0.21
2.3	3.37	0.4	1.09	1.47	0.17
1.8	2.8	3.8	1.68	1.56	2.11
5.58	7.8	0.31	0.92	1.43	1.40	0.16	1.45	0.06	2.63
PIMUZ 31510, section 3	4.88 3.86	7 5	0.85 0.8	1.60 1.58	1.43 1.30	0.17 0.21	0.60	2.43
2.43	3.7	0.66	1.03	1.52	0.27

Fig. 2. Juvenile (neanic) specimens of Goniatites lazarus Korn, Klug, and Mapes, 2005 , Entogonites saharensis Korn, Klug, and Mapes, 2005 , and Entogonites bucheri sp. nov. All from the early late Viséan, 12 km SE of Dar Kaoua (Tafilalt, Morocco). A . PIMUZ 31512, two neanic G. lazarus specimens (white arrows) in ventral views (A 1 ), note the associated E. saharensis and orthocones. Enlarged G. lazarus in lateral view (A 2 ); the narrow umbilicus and the umbilical ridge (A 3 ). B . PIMUZ 31512, a juvenile G. lazarus , a small juvenile and a subadult E. saharensis ; G. lazarus in ventral (B 1 ) and lateral (B 2 ) views. C . PIMUZ 31520, detail of a fully grown Maxigoniatites saourensis ( Pareyn, 1961 ) with G. lazarus , 3 juvenile E. saharensis , and a subadult E. saharensis and a hatchling of E. bucheri sp. nov. (arrowed); C 2 , detail of C 1 , showing G. lazarus and E. bucheri sp. nov. All specimens whitened with NH 4 Cl-sublimate. Scale bars 10 mm. Description .—At diameters of 2–7 mm , the whorl width/diameter ratio ranges between 1.4 and almost 1.8 (e.g., PIMUZ 31512; Figs. 2–4 ; Table 2 ). This ratio lies between 1.4 and 1 in later ontogeny (dm < 70 mm ) and further decreases to 0.6 in the still pachyconic adults (PIMUZ 31514, dm 97 mm ; Table 2 ). The umbilicus is very narrow throughout the post-hatching ontogeny. Until a diameter of about 7 mm , the spindle-shaped shell carries an umbilical ridge (PIMUZ 31512; Fig. 2A 3 ). Adult conchs are globose with rounded venter and very involute (PIMUZ 31514; Fig. 3 ). Ornamentation is limited to fine growth lines, which are rather straight in small juveniles (e.g., PIMUZ 31520; Fig. 2C 2 ) and can be slightly crenulated in adults (PIMUZ 31514). In PIMUZ 31515, the crenulation consists of 2 minute waves on the growth lines or lirae, which are spaced at 0.5–0.8 mm at a diameter of 85 mm . The juvenile suture is poorly visible in PIMUZ 31512; its overall course corresponds to the adult suture, but details are not visible in all juvenile specimens. The adult suture (PIMUZ 31514; Fig. 3 ) was examined at ca. 77 mm diameter. At this size, the V-shaped external lobe is almost twice as high as wide at the mid of its height. The median saddle measures 0.36 of the E-lobe height. The ventrolateral saddle has a nearly isosceles triangle-shape with shallow bulges near the bases and tops of both flanks and gentle concavity in the middle. Its adapertural tip is slightly asymmetrical and narrowly rounded. The adventive lobe is similar in size and shape, except that it is somewhat lower and broader. Fig. 3. Adult specimen of Goniatites lazarus Korn, Klug, and Mapes, 2005 (PIMUZ 31514) from the early late Viséan, 12 km SE of Dar Kaoua (Tafilalt, Morocco), in dorsal ( A ), lateral ( B ), and ventral ( C ) views. All specimens whitened with NH 4 Cl-sublimate Fig. 4. Comparison of cross sections, measurements, and ratios of Goniatites lazarus and other ammonoids. A . Goniatites lazarus , subadult (MB.C. 25130, A 1 ) and juvenile (PIMUZ 31510, A 2 ) from early late Viséan, 12 km SE of Dar Kaoua (Tafilalt, Morocco). B . Goniatites fimbriatus , MB.C. 13299 (after Korn et al. 2008: fig. 23A) from Nehden, Viséan, Rhenish Mountains, Germany. C . Juvenile Kornia citrus , MB.C. 10202.1 (after Ebbighausen and Bockwinkel 2007 : fig. 30B) from early Tournaisian, Aguelmous (Tafilalt, Morocco); note the conch shape and umbilical ridge, which is similar to juvenile G. lazarus . Whorl width (ww) and umbilical width (uw) indexes ( D ) and whorl expansion rate (WER) ( E ) of G. lazarus , G. fimbriatus , and K. citrus . Remarks .—The inner whorls of G. lazarus strongly resemble those of Kornia citrus Bockwinkel and Ebbighausen, 2006 . We cut and polished two subadult G. lazarus from the same locality ( Fig. 4A ), which confirmed that the spindle-shaped juveniles indeed belong to this species and not to Kornia . With a conch width index (ww/dm) of up to 1.8, juveniles of this species belong to the ammonoids with the most extreme whorl width/diameter ratio. Similar changes in conch ontogeny have been documented from several goniatitids including, e.g., G. fimbriatus ( Fig. 4B ) and K. citrus ( Fig. 4C ). Stratigraphic and geographic range .—Early late Viséan, so far only known from the Tafilalt ( Morocco ).