Add the Ann Arbor RR to the list as one of the seven independent roads that made up Conrail.
The full list of companies (mostly subsidiaries of the big seven) that were transferred to Conrail is more substantial than I'd have guessed, and includes a lot of road names I've never heard of.
Source; Wikipedia:

Allentown Terminal Railroad... CNJ
Ann Arbor Railroad... AA
Baltimore and Eastern Railroad... PC (PRR)
Bay Shore Connecting Railroad... CNJ/LV
Beech Creek Railroad... PC (NYC)
Buffalo Creek Railroad... EL (Erie)/LV Merged on December 31, 1983[4]
Central Indiana Railway... PC (NYC/PRR)
Central Railroad of New Jersey... CNJ
Central Railroad of Pennsylvania... CNJ No real property conveyed
Chicago, Kalamazoo and Saginaw Railway... PC (NYC)
Chicago River and Indiana Railroad... PC (NYC)
Cleveland and Pittsburgh Railroad... PC (PRR)
Cleveland, Cincinnati, Chicago and St. Louis Railway... PC (NYC)
Connecting Railway... PC (PRR)
Dayton Union Railway... PC (NYC/PRR)
Delaware Railroad... PC (PRR)
Delaware and Bound Brook Railroad... RDG
Detroit Manufacturers Railroad... PC (NYC)
Dover and Rockaway Railroad... CNJ
East Pennsylvania Railroad... RDG
Erie and Kalamazoo Railroad... PC (NYC)
Erie Lackawanna Railway... EL (Erie/DL&W)
Erie and Pittsburgh Railroad... PC (PRR)
Fort Wayne and Jackson Railroad... PC (NYC)
Holyoke and Westfield Railroad... PC (NH)
Hudson River Bridge Company at Albany... PC (NYC)
Indianapolis Union Railway PC (NYC/PRR)
Ironton Railroad... LV
Joliet and Northern Indiana Railroad... PC (NYC)
Kalamazoo, Allegan and Grand Rapids Railroad... PC (NYC)
Lackawanna and Wyoming Valley Railway... EL (DL&W)
Lehigh and Hudson River Railway... L&HR
Lehigh and New England Railway... CNJ
Lehigh Valley Railroad... LV
Little Miami Railroad... PC (PRR)
Mahoning Coal Railroad... PC (NYC)
Mahoning and Shenango Valley Company... PC (NYC)
Michigan Central Railroad... PC (NYC)
Mount Hope Mineral Railroad... CNJ
New York Connecting Railroad... PC (NH/PRR)
New York and Long Branch Railroad... PC (PRR)/CNJ
Niagara Junction Railway... EL (Erie)/LV/PC (NYC)
North Brookfield Railroad... PC (NH)
North Pennsylvania Railroad... RDG
Northern Central Railway... PC (PRR)
Norwich and Worcester Railroad... PC (NH)
Penn Central Transportation Company... PC (NYC/PRR/NH)
Penndel Company... PC (NYC/PRR) Successor to a number of non-operating subsidiaries
Pennsylvania and Atlantic Railroad... PC (PRR)
Pennsylvania–Reading Seashore Lines... PC (PRR)/RDG
Pennsylvania Tunnel and Terminal Railroad... PC (PRR)
Peoria and Eastern Railway... PC (NYC)
Philadelphia, Baltimore and Washington Railroad... PC (PRR)
Philadelphia, Germantown and Norristown Railroad... RDG
Philadelphia and Trenton Railroad... PC (PRR)
Pittsburgh, Fort Wayne and Chicago Railway... PC (PRR)
Pittsburgh, Youngstown and Ashtabula Railway PC (PRR)
Plymouth Railroad... RDG
Port Reading Railroad... RDG
Raritan River Railroad... PC (PRR)/CNJ Merged in April 1980[3]
Reading Company... RDG
Rochester and Genesee Valley Railroad... EL (Erie)
Shamokin Valley and Pottsville Railroad... PC (PRR)
South Manchester Railroad... PC (NH)
Trenton–Princeton Traction Company... RDG
Troy and Greenbush Railroad... PC (NYC)
Union Depot Company (Columbus, Ohio)... PC (NYC/PRR)
Union Railroad of Baltimore... PC (PRR)
United New Jersey Railroad and Canal Company... PC (PRR)
Waynesburg Southern Railroad... PC (PRR)
Waynesburg and Washington Railroad... PC (PRR)
West Jersey and Seashore Railroad... PC (PRR)/RDG
Wharton and Northern Railroad... CNJ
Wilmington and Northern Railroad... RDG
American Contract Company... PC No real property conveyed
Communipaw Central Land Company... CNJ
Consolidated Real Estate Company... LV
Despatch Shops, Inc.... PC
Eastern Real Estate Company... RDG
Erie Land and Improvement Company... EL (Erie)
Erie Land and Improvement Company of Pennsylvania... EL (Erie)
Hoboken Ferry Company... EL (DL&W)
Hudson Realty Company... EL
Lawroy Land Company... EL
Manor Real Estate Company... PC
New York Central Development Corporation... PC
Penndiana Improvement Corporation... PC
Providence Produce Warehouse Company PC
United Real Estate Company... LV