Important public safety announcement;
Crocodiles today are a somewhat depauperate group compared with the huge variety in the fossil record. But then again, what we see alive today is only a snapshot, while the superfamily has a record back some 230 Million Years, into the Triassic.
As crocodiles (and alligators, etc) may be a little one-dimensional in RPGs (either floating logs to ambush boat trips, ambushes from river banks, or giant monsters that ambush elephants), here's two different species with their roots in the fossil record.
So, this was a HUGE crocodile that lived in the Sahara Region during the Upper Cretaceous. 20 feet (7 metres) long, with stereoscopic vision and long, powerful legs, it is a vicious carnivore with an armoured snout for ramming and several sets of large, ripping boar like teeth.
Combined with the fused plates of armour-like hide on it's head, back and sides, it's a nasty surprise for travellers off the beaten path, as it avoids swampy land and inhabits rocky canyons and scattered woodlands, ambushing and chasing down anything that it thinks it can catch. Doesn't usually go after anything less than horse sized as they generally aren't worth eating, although a band of adventurers making plenty of noise would both attract it's attention and be worth the effort. By far the most attractive meal would be a small troop of mounted guard...
The Kappra exist in my campaign near a southern kingdom called Celise, in wild, sparsely wooded lands beyond the settlements, between the Great Swamp and an encircling mountain range. They are territorial, and generally hang around a large sunbathed rock slab or outcrop, where they sun themselves when not out hunting. A 6 mile hex gives an area of 31 square miles, more or less, which is 80 square km, so I'm giving each of these around 3 hexes as a territory. They are cunning predators that actively stalk prey, and rush likely targets from gullies, under bridges or copses. They have been seen attacking injured wyverns on high mountain slopes, but must descend before night falls to maintain their body heat.
Dragon Warrior Stats (as it's really the only system I'm familiar enough with to do this - for other systems, I'm basically crossing a wild boar with a wyvern); The hide of one slain can be used to make armour that encumbers like plate, provides the protection of chainmail, but doesn't disrupt spell casting, so they are somewhat sought after by sorcerers.
ATTACK 22 Bite (d8+2,6); Snout Ram (d10)
DEFENCE 5 Armour Factor 4
MAGICAL DEFENCE 8
EVASION 4 Stealth 15 Perception 9
4d6+12 Heath Points
Otherwise known as Dogcroc, this little creature is around 3 feet long, with a soft, doglike snout and canine-lie teeth. It eats tubers, berries, small animals and carrion, and generally fills the ecological niche of wild dogs in borderlands and civilised areas of Celise, the same southern kingdom mentioned above. A capable runner and excellent swimmer, they are common pets amongst hunters, sailors and nobles, but not farmers, as they tend to uncontrollably attack and kill chickens and other feathered animals. Strangely, they are completely safe around human (and other civilised people's) babies and children.
Packs of Arapes do skulk through borderland areas, preying mostly on birds and any other injured animals, as well as fruits and tubers. Strangely, even these creatures will not attack children, and will actively defend them against violence or exposure. There are stories of abandoned children raised by packs, and in Celise society, this type of upbringing is strangely seen as blessed by the All-Mother.
ATTACK 13 Bite (d4,4)
DEFENCE 4 Armour Factor 2
MAGICAL DEFENCE 3
EVASION 4 Stealth 16 Perception 11
1d6+4 Health Points
Here's a National Geographic video about the fossils - see about 2:00 for the Kappra!