Frontier Mastodon — ruling 1

Frontier Mastodon's ferocious ability checks if you control a creature with power 4 or greater as Frontier Mastodon enters the battlefield. Because Frontier Mastodon isn't on the battlefield at this time, it won't count itself.

Frontier Mastodon : règles, fonctionnement et interactions (MTG)

Frontier Mastodon is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Ferocious — This creature enters with a +1/+1 counter on it if you control a creature with power 4 or greater.

How it works : Frontier Mastodon

Original English text — Wizards of the Coast / Scryfall

#1November 24, 2014· Wizards of the Coast
Frontier Mastodon's ferocious ability checks if you control a creature with power 4 or greater as Frontier Mastodon enters the battlefield. Because Frontier Mastodon isn't on the battlefield at this time, it won't count itself.
No other card is named in this ruling.