530:
516:
147:
351:
542:
808:
123:
325:
The biology of the heteromorph ammonites is not clear, but one certainty is that their uncoiled shells would have made these forms very poor swimmers. Open shells, particularly ones with spines and ribs, create a lot of drag; but more importantly, the orientation of the shell, with the body hanging
403:
In the more primitive forms, the shell departs only slightly from being a perfect spiral, with only the last, outermost whorl being open, forming a hook underneath the main spiral. In such forms the spiral was the chambered,
305:
period, when they rapidly diversified and became one of the most distinctive components of
Cretaceous marine faunas. They have been recorded from every continent and many are used as zonal or
445:
Many of the earlier heteromorph forms had regularly coiled shells barely distinguishable from the homomorph ammonites (for example, the Lower
Cretaceous genus
787:
Pasch, A. D., K. C. May. 2001. Taphonomy and paleoenvironment of hadrosaur (Dinosauria) from the
Matanuska Formation (Turonian) in South-Central Alaska. In:
326:
below the buoyant part of the shell, would have created a serious impediment to efficient swimming. It's more likely these ammonites either drifted in the
929:
919:
529:
934:
376:, which could grow to 1β2 m (3.3β6.6 ft) in length. Some species were very widely distributed, for example some species of
779:
408:
part of the shell, and the hook was the living chamber in which the soft body of the ammonite resided. Examples of such types were
438:
were much larger but had a similar sort of shape, though the shafts were open so that the whole thing looked rather like a big
914:
146:
490:, which looked more like a ball of string than anything else. Some forms combined different coiling modes. For example,
451:). Some offshoots of the uncoiled varieties even went back to being regularly coiled. Most notable among these were the
432:
consisted of three or four shafts squashed together and connected with tight, 180 degree bends. Members of the genus
924:
812:
309:. The most distinctive feature of the majority of the Ancyloceratina is the tendency for most of them to have
909:
397:
824:
463:
and their relatives, which were mostly regular spirals in shape except for a very slight hook at the end.
656:
260:
881:
674:
515:
507:
The thin shelled heteromorphic ammonites probably lived at depths 36β183 m (118.1β600.4 ft).
662:
610:
313:
that are not regular spirals like most other ammonites. These irregularly-coiled ammonites are called
767:
636:
628:
604:
270:
642:
416:
862:
616:
580:
232:
474:
447:
668:
428:
141:
886:
466:
The Late
Cretaceous enjoyed the widest variety of heteromorphs, including the straight-shelled
775:
791:. Ed.s Tanke, D. H., Carpenter, K., Skrepnick, M. W. Indiana University Press. Pages 219β236.
338:, or else they crawled along the sea floor feeding on sessile or slow-moving animals such as
714:
622:
562:
255:
586:
574:
434:
132:
801:
726:
702:
648:
598:
568:
459:
903:
696:
520:
385:
265:
73:
732:
682:
426:. The more advanced heteromorphs departed from such forms radically. The shells of
372:
317:, in contrast to regularly coiled ammonites, which are called homomorph ammonites.
306:
294:
275:
237:
802:
Scientific report on the functional morphology of
Cretaceous heteromorph ammonites
856:
708:
688:
592:
410:
350:
310:
48:
541:
534:
492:
486:
480:
439:
393:
302:
214:
201:
188:
93:
58:
17:
847:
720:
546:
468:
453:
389:
355:
335:
158:
113:
98:
42:
873:
807:
841:
422:
405:
331:
327:
298:
290:
178:
109:
88:
83:
68:
63:
53:
381:
103:
78:
168:
818:
772:
Heteromorph: The rarest fossil ammonites. Nature at its most bizarre
122:
540:
528:
514:
349:
339:
822:
362:
Ancyloceratida varied widely in size, ranging from diminutive
753:"Paleoecologic Context," Pasche and May (2001); page 224.
500:, but had a planar hook hanging underneath, more like an
400:
that covered much of the US, were much more localized.
366:, which was barely 3 cm (1.2 in) long, to
831:
293:most closely related to the ammonites of order
358:heteromorph ammonites from southeastern France
8:
130:A reconstruction of a heteromorph ammonite,
819:
121:
31:
746:
7:
396:. Others, like those inhabiting the
330:, collecting small animals on long
301:but were not very common until the
25:
806:
496:started off with a helix like a
145:
930:Late Jurassic first appearances
297:. They evolved during the Late
525:with spines partially restored
1:
27:Extinct suborder of ammonites
920:Prehistoric animal suborders
289:were a diverse suborder of
951:
935:Maastrichtian extinctions
774:, At One Communications,
252:
247:
142:Scientific classification
140:
129:
120:
34:
789:Mesozoic Vertebrate Life
478:; the helically coiled
398:Western Interior Seaway
551:
538:
526:
359:
882:Paleobiology Database
544:
532:
518:
353:
315:heteromorph ammonites
915:Ammonitida suborders
815:at Wikimedia Commons
535:Nipponites mirabilis
657:Douvilleiceratoidea
261:Douvilleiceratoidea
669:Douvilleiceratidae
552:
539:
527:
484:; and the bizarre
360:
925:Mollusc suborders
897:
896:
825:Taxon identifiers
811:Media related to
675:Trochleiceratidae
283:
282:
243:
16:(Redirected from
942:
890:
889:
877:
876:
867:
866:
865:
852:
851:
850:
820:
810:
784:
754:
751:
715:Diplomoceratidae
663:Astiericeratidae
623:Macroscaphitidae
611:Himantoceratidae
563:Ancyloceratoidea
380:can be found in
256:Ancyloceratoidea
241:
231:
226:
213:
200:
150:
149:
125:
108:
45:
41:199.6β64.8
38:Temporal range:
32:
21:
950:
949:
945:
944:
943:
941:
940:
939:
900:
899:
898:
893:
885:
880:
872:
870:
861:
860:
855:
846:
845:
840:
827:
798:
782:
768:Wolfgang Grulke
766:
763:
758:
757:
752:
748:
743:
637:Deshayesitoidea
629:Ptychoceratidae
605:Heteroceratidae
587:Crioceratitidae
575:Ancyloceratidae
513:
348:
323:
271:Deshayesitoidea
235:
230:
224:
211:
198:
144:
116:
107:
106:
101:
96:
91:
86:
81:
76:
71:
66:
61:
56:
51:
40:
39:
36:
28:
23:
22:
15:
12:
11:
5:
948:
946:
938:
937:
932:
927:
922:
917:
912:
910:Ancyloceratina
902:
901:
895:
894:
892:
891:
878:
868:
863:Ancyloceratina
853:
837:
835:
833:Ancyloceratina
829:
828:
823:
817:
816:
813:Ancyloceratina
804:
797:
796:External links
794:
793:
792:
785:
780:
762:
759:
756:
755:
745:
744:
742:
739:
738:
737:
736:
735:
729:
727:Nostoceratidae
723:
717:
711:
705:
703:Anisoceratidae
693:
692:
691:
679:
678:
677:
671:
665:
653:
652:
651:
649:Parahoplitidae
645:
643:Deshayesitidae
633:
632:
631:
625:
619:
613:
607:
601:
599:Hemihoplitidae
595:
589:
583:
577:
571:
569:Acrioceratidae
556:Ancyloceratina
512:
511:Classification
509:
460:Hoploscaphites
417:Protanisoceras
354:Assemblage of
347:
344:
322:
319:
287:Ancyloceratina
281:
280:
279:
278:
273:
268:
263:
258:
250:
249:
248:Superfamilies
245:
244:
228:Ancyloceratina
222:
218:
217:
209:
205:
204:
196:
192:
191:
186:
182:
181:
176:
172:
171:
166:
162:
161:
156:
152:
151:
138:
137:
127:
126:
118:
117:
102:
97:
92:
87:
82:
77:
72:
67:
62:
57:
52:
47:
46:
37:
35:Ancyloceratina
26:
24:
18:Ancyloceratida
14:
13:
10:
9:
6:
4:
3:
2:
947:
936:
933:
931:
928:
926:
923:
921:
918:
916:
913:
911:
908:
907:
905:
888:
883:
879:
875:
869:
864:
858:
854:
849:
843:
839:
838:
836:
834:
830:
826:
821:
814:
809:
805:
803:
800:
799:
795:
790:
786:
783:
781:9780992974008
777:
773:
769:
765:
764:
760:
750:
747:
740:
734:
730:
728:
724:
722:
718:
716:
712:
710:
706:
704:
700:
699:
698:
697:Turrilitoidea
694:
690:
686:
685:
684:
680:
676:
672:
670:
666:
664:
660:
659:
658:
654:
650:
646:
644:
640:
639:
638:
634:
630:
626:
624:
620:
618:
617:Labeceratidae
614:
612:
608:
606:
602:
600:
596:
594:
590:
588:
584:
582:
581:Bochianitidae
578:
576:
572:
570:
566:
565:
564:
560:
559:
558:
557:
549:
548:
543:
537:
536:
531:
524:
522:
521:Crioceratites
517:
510:
508:
505:
503:
499:
495:
494:
489:
488:
483:
482:
477:
476:
471:
470:
464:
462:
461:
456:
455:
450:
449:
443:
441:
437:
436:
431:
430:
425:
424:
419:
418:
413:
412:
407:
401:
399:
395:
391:
387:
386:South America
383:
379:
375:
374:
369:
365:
357:
352:
345:
343:
341:
337:
333:
329:
320:
318:
316:
312:
308:
307:index fossils
304:
300:
296:
292:
288:
277:
274:
272:
269:
267:
266:Turrilitoidea
264:
262:
259:
257:
254:
253:
251:
246:
239:
234:
229:
223:
220:
219:
216:
210:
207:
206:
203:
197:
194:
193:
190:
187:
184:
183:
180:
177:
174:
173:
170:
167:
164:
163:
160:
157:
154:
153:
148:
143:
139:
135:
134:
128:
124:
119:
115:
111:
105:
100:
95:
90:
85:
80:
75:
70:
65:
60:
55:
50:
44:
33:
30:
19:
832:
788:
771:
749:
733:Turrilitidae
695:Superfamily
683:Scaphitoidea
681:Superfamily
655:Superfamily
635:Superfamily
561:Superfamily
555:
553:
545:
533:
519:
506:
501:
497:
491:
485:
479:
475:Sciponoceras
473:
467:
465:
458:
452:
448:Deshayesites
446:
444:
433:
427:
421:
415:
409:
402:
377:
373:Diplomoceras
371:
367:
363:
361:
334:like modern
324:
314:
295:Lytoceratina
286:
284:
276:Scaphitoidea
227:
131:
29:
857:Wikispecies
709:Baculitidae
689:Scaphitidae
593:Hamulinidae
502:Ancyloceras
429:Ptychoceras
411:Ancyloceras
364:Ptychoceras
236: [
189:Cephalopoda
904:Categories
761:References
498:Turrilites
493:Nostoceras
487:Nipponites
481:Turrilites
440:paper clip
394:Antarctica
346:Morphology
303:Cretaceous
221:Suborder:
215:Ammonitida
202:Ammonoidea
195:Subclass:
741:Footnotes
721:Hamitidae
554:Suborder
547:Scaphites
469:Baculites
454:Scaphites
390:Australia
368:Baculites
356:Barremian
336:jellyfish
332:tentacles
165:Kingdom:
159:Eukaryota
114:Paleocene
871:BioLib:
842:Wikidata
770:(2014),
423:Tropaeum
328:plankton
299:Jurassic
291:ammonite
233:Wiedmann
179:Mollusca
175:Phylum:
169:Animalia
155:Domain:
110:Jurassic
848:Q290948
731:Family
725:Family
719:Family
713:Family
707:Family
701:Family
687:Family
673:Family
667:Family
661:Family
647:Family
641:Family
627:Family
621:Family
615:Family
609:Family
603:Family
597:Family
591:Family
585:Family
579:Family
573:Family
567:Family
435:Hamites
406:buoyant
382:Eurasia
378:Hamites
321:Biology
208:Order:
185:Class:
133:Hamites
887:129198
874:800812
778:
523:nolani
420:, and
392:, and
311:shells
242:, 1966
340:clams
240:]
776:ISBN
472:and
370:and
285:The
136:sp.
49:Preκ
550:sp.
906::
884::
859::
844::
504:.
457:,
442:.
414:,
388:,
384:,
342:.
238:de
112:-
99:Pg
43:Ma
225:β
212:β
199:β
104:N
94:K
89:J
84:T
79:P
74:C
69:D
64:S
59:O
54:κ
20:)
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
