Rex Energy 10-K/A 2008 FY Annual report (amended)

Exhibit 21.1

Subsidiaries of Rex Energy Corporation

at December 31, 2008

Name	Entity Type	Jurisdiction of Incorporation or Formation	Percentage Ownership
Rex Energy I, LLC	Limited Liability Company	Delaware	100	%
Rex Energy Marketing, LLC	Limited Liability Company	Delaware	100	%(1)
Rex Energy Operating Corp.	Corporation	Delaware	100	%
Rex Energy IV, LLC	Limited Liability Company	Delaware	100	%
PennTex Resources Illinois, Inc.	Corporation	Delaware	100	%
Penn Tex Energy, Inc.	Corporation	Delaware	100	%
PennTex Resources, L.P.	Limited Partnership	Texas	100	%(2)
R.E. Gas Development, LLC	Limited Liability Company	Delaware	100	%
Central Pennsylvania Water Treatment, LLC	Limited Liability Company	Delaware	100	%

(1) Rex Energy Marketing, LLC is a wholly owned subsidiary of Rex Energy I, LLC.

(2) Rex Energy Corporation owns a 99% limited partnership interest in PennTex Resources, L.P. The 1% general partner interest of PennTex Resources, L.P. is owned by Penn Tex Energy, Inc.