The document provides morphological descriptions of various nautiloid cephalopods, including Nautilus and Orthoceras, detailing their shell shapes, structures, and geological ages ranging from the Triassic to the Cretaceous. It categorizes these organisms within the Kingdom Animalia, Phylum Mollusca, and specific classifications in the subclass Diabranchia and order Belemnitida. Additionally, it offers contact information for further paleontology practical sessions.

1. Morphological characters –
▪ Shell is Globular and involute coiling
▪ Few whorls with large body chamber,
Aperture is oval and rarely semilunar
▪ Umbilicus may be occluded with callus.
▪ Central siphuncle is present with septal
neck-retrosiphonate.
▪ Shows simple nauitiloid suture line, thin
growth lines and simple ribs.
Geological Age – Triassic to recent
Morphological Characters –
▪ Shell is straight, subcylindrical orthocone
slightly expanding with straight coiling.
▪ Umbilicus is absent.
▪ Shows circular aperture, subcentral siphuncle
and retrosiphonate septal neck.
▪ Suture line is simple and smooth
ornamentation lines.
Geological Age – Carboniferous to Triassic.
GL- 201 P a l a e n t o l o g y
QUARTZ- Exclusive Coaching Institute for Earth Sciences Nikhil V. Sherekar
Practical
Classification
Kingdom Animalia
Sub kingdom Invertibrata
Phylum Mollusca
Class Cephalopoda
Order Nautiloidea
Genus Nautilus
GL- 201 P a l a e n t o l o g y
QUARTZ- Exclusive Coaching Institute for Earth Sciences Nikhil V. Sherekar
Practical
Classification
Kingdom Animalia
Sub kingdom Invertibrata
Phylum Mollusca
Class Cephalopoda
Order Nautiloidea
Genus Orthoceras

2. Morphological Characters –
▪ Shell is Cigar – shaped long, conical with longitudinal groove.
▪ Guard is tapered at the posterior end with a deep conical cavity.
▪ In transverse section guard shows a fibrous structure with tiny
calcite radiating prisms, concentric rings about this point denotes
growth stages.
▪ Phragmocone is weakly calcified or absent in fossil. It is conical,
chambered shell with thin delicated walls. Perforated by the
ventrally situated siphuncle.
▪ The posterior end with oval protoconch at its tip, lies within the alveolus of the guard.
▪ Pro-ostracum is a projection on a dorsal side of phragmocone forming a protective shield over the visceral
mass of the animal. Rare in fossilised specimen.
▪ Ornamentations are smooth.
Geological Age – Lower Carboniferous to Cretaceous.
GL- 201 P a l a e n t o l o g y
QUARTZ- Exclusive Coaching Institute for Earth Sciences Nikhil V. Sherekar
Practical
Classification
Kingdom Animalia
Sub kingdom Invertibrata
Phylum Mollusca
Class Cephalopoda
Subclass Diabranchia
Order Belemnitida
Genus Belemnite
For more Palaentology Practical's contact Nikhil Sherekar - 8390377801