[PF]What's the source of this table?

[isildur]

http://www.d20pfsrd.com/classes/core-classes/druid/animal-companions#TOC-Animal-Choices

There are mentions about ranger, padadin animal companion restriction, but there are no mentions in core rule book.

[gartius]

CRB pg 66

A ranger who selects an animal
companion can choose from the following list: badger,
bird, camel, cat (small), dire rat (see the Pathfinder RPG
Bestiary), dog, horse, pony, snake (viper or constrictor),
or wolf.

and CRB pg 63

The second type of bond allows a paladin to gain the
service of an unusually intelligent, strong, and loyal
steed to serve her in her crusade against evil. This mount
is usually a heavy horse (for a Medium paladin) or a pony
(for a Small paladin), although more exotic mounts,
such as a boar, camel, or dog are also suitable.

the srd has extrapolated for ease of use

[Bigbeefie]

Basically the Website has compiled all the Pathfinder resources so you the player can easily find what you need and the information from all the books on the subject.

[Psyren]

Basically the Website has compiled all the Pathfinder resources so you the player can easily find what you need and the information from all the books on the subject.

That. The various Bestiaries and some other books added more options so the PFSRD put them all in one place. For example, A Roc companion requires reading the Roc entry in the Bestiary.